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Hard water
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Not to be confused with heavy water.
A bathtub faucet with built-up calcification from hard water.
Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone and chalk which are largely made up of calcium and magnesium carbonates.
Hard drinking water may have moderate health benefits, but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling towers, and other equipment that handles water. In domestic settings, hard water is often indicated by a lack of foam formation when soap is agitated in water, and by the formation of limescale in kettles and water heaters.[1] Wherever water hardness is a concern, water softening is commonly used to reduce hard water's adverse effects.
Contents
[hide]
1 Sources of hardness
1.1 Temporary hardness
1.2 Permanent hardness
2 Effects
2.1 Softening
2.2 Health considerations
3 Measurement
3.1 Hard/soft classification
3.2 Indices
3.2.1 Langelier saturation index (LSI)
3.2.2 Ryznar Stability Index (RSI)
3.2.3 Puckorius Scaling Index (PSI)
3.2.4 Other indices
4 Regional information
4.1 In Australia
4.2 In Canada
4.3 In England and Wales
4.4 In Ireland
4.5 In the United States
5 See also
6 References
7 External links
Sources of hardness[edit]
Water's hardness is determined by the concentration of multivalent cations in the water. Multivalent cations are positively charged metal complexes with a charge greater than 1+. Usually, the cations have the charge of 2+. Common cations found in hard water include Ca2+ and Mg2+. These ions enter a water supply by leaching from minerals within an aquifer. Common calcium-containing minerals are calcite and gypsum. A common magnesium mineral is dolomite (which also contains calcium). Rainwater and distilled water are soft, because they contain few ions.[2]
The following equilibrium reaction describes the dissolving and formation of calcium carbonate :
CaCO3 (s) + CO2 (aq) + H2O (l) ⇋ Ca2+ (aq) + 2HCO3− (aq)
The reaction can go in either direction. Rain containing dissolved carbon dioxide can react with calcium carbonate and carry calcium ions away with it. The calcium carbonate may be re-deposited as calcite as the carbon dioxide is lost to atmosphere, sometimes forming stalactites and stalagmites.
Calcium and magnesium ions can sometimes be removed by water softeners.[3]
Temporary hardness[edit]
See also: Carbonate hardness
Temporary hardness is a type of water hardness caused by the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate). When dissolved, these minerals yield calcium and magnesium cations (Ca2+, Mg2+) and carbonate and bicarbonate anions (CO32−, HCO3−). The presence of the metal cations makes the water hard. However, unlike the permanent hardness caused by sulphate and chloride compounds, this "temporary" hardness can be reduced either by boiling the water, or by the addition of lime (calcium hydroxide) through the process of lime softening.[4] Boiling promotes the formation of carbonate from the bicarbonate and precipitates calcium carbonate out of solution, leaving water that is softer upon cooling.
Permanent hardness[edit]
Permanent hardness is hardness (mineral content) that cannot be removed by boiling. When this is the case, it is usually caused by the presence of calcium sulphate/calcium chloride and/or magnesium sulphate/magnesium chloride in the water, which do not precipitate out as the temperature increases. Ions causing permanent hardness of water can be removed using a water softener, or ion exchange column.
Total Permanent Hardness = Permanent Calcium Hardness + Permanent Magnesium Hardness
Effects[edit]
With hard water, soap solutions form a white precipitate (soap scum) instead of producing lather, because the 2+ ions destroy the surfactant properties of the soap by forming a solid precipitate (the soap scum). A major component of such scum is calcium stearate, which arises from sodium stearate, the main component of soap:
2 C17H35COO− (aq) + Ca2+ (aq) → (C17H35COO)2Ca (s)
Hardness can thus be defined as the soap-consuming capacity of a water sample, or the capacity of precipitation of soap as a characteristic property of water that prevents the lathering of soap. Synthetic detergents do not form such scums.
A portion of the ancient Roman Eifel aqueduct in Germany. In service for about 180 years, the aqueduct had deposits of scale up to 20 cm thick along the walls.
Hard water also forms deposits that clog plumbing. These deposits, called "scale", are composed mainly of calcium carbonate (CaCO3), magnesium hydroxide (Mg(OH)2), and calcium sulfate (CaSO4).[2] Calcium and magnesium carbonates tend to be deposited as off-white solids on the inside surfaces of pipes and heat exchangers. This precipitation (formation of an insoluble solid) is principally caused by thermal decomposition of bicarbonate ions but also happens in cases where the carbonate ion is at saturation concentration.[5] The resulting build-up of scale restricts the flow of water in pipes. In boilers, the deposits impair the flow of heat into water, reducing the heating efficiency and allowing the metal boiler components to overheat. In a pressurized system, this overheating can lead to failure of the boiler.[6] The damage caused by calcium carbonate deposits varies on the crystalline form, for example, calcite or aragonite.[7]
The presence of ions in an electrolyte, in this case, hard water, can also lead to galvanic corrosion, in which one metal will preferentially corrode when in contact with another type of metal, when both are in contact with an electrolyte. The softening of hard water by ion exchange does not increase its corrosivity per se. Similarly, where lead plumbing is in use, softened water does not substantially increase plumbo-solvency.[8]
In swimming pools, hard water is manifested by a turbid, or cloudy (milky), appearance to the water. Calcium and magnesium hydroxides are both soluble in water. The solubility of the hydroxides of the alkaline-earth metals to which calcium and magnesium belong (group 2 of the periodic table) increases moving down the column. Aqueous solutions of these metal hydroxides absorb carbon dioxide from the air, forming the insoluble carbonates, giving rise to the turbidity. This often results from the pH being excessively high (pH > 7.6). Hence, a common solution to the problem is, while maintaining the chlorine concentration at the proper level, to lower the pH by the addition of hydrochloric acid, the optimum value being in the range of 7.2 to 7.6.
Softening[edit]
Main article: Water softening
It is often desirable to soften hard water. Most detergents contain ingredients that counteract the effects of hard water on the surfactants. For this reason, water softening is often unnecessary. Where softening is practised, it is often recommended to soften only the water sent to domestic hot water systems so as to prevent or delay inefficiencies and damage due to scale formation in water heaters. A common method for water softening involves the use of ion exchange resins, which replace ions like Ca2+ by twice the number of monocations such as sodium or potassium ions.
Washing soda (sodium carbonate - Na2CO3) is easily obtained and has long been used as a water softener for domestic laundry, in conjunction with the usual soap or detergent.
Health considerations[edit]
The World Health Organization says that "there does not appear to be any convincing evidence that water hardness causes adverse health effects in humans".[1] In fact, the United States National Research Council has found that hard water actually serves as a dietary supplement for calcium and magnesium.[9]
Some studies have shown a weak inverse relationship between water hardness and cardiovascular disease in men, up to a level of 170 mg calcium carbonate per litre of water. The World Health Organization has reviewed the evidence and concluded the data was inadequate to allow for a recommendation for a level of hardness.[1]
Recommendations have been made for the maximum and minimum levels of calcium (40–80 ppm) and magnesium (20–30 ppm) in drinking water, and a total hardness expressed as the sum of the calcium and magnesium concentrations of 2–4 mmol/L.[10]
Other studies have shown weak correlations between cardiovascular health and water hardness.[11][12][13]
Some studies correlate domestic hard water usage with increased eczema in children.[14][15][16][17]
The Softened-Water Eczema Trial (SWET), a multicenter randomized controlled trial of ion-exchange softeners for treating childhood eczema, was undertaken in 2008. However, no meaningful difference in symptom relief was found between children with access to a home water softener and those without.[18]
Measurement[edit]
Hardness can be quantified by instrumental analysis. The total water hardness is the sum of the molar concentrations of Ca2+ and Mg2+, in mol/L or mmol/L units. Although water hardness usually measures only the total concentrations of calcium and magnesium (the two most prevalent divalent metal ions), iron, aluminium, and manganese can also be present at elevated levels in some locations. The presence of iron characteristically confers a brownish (rust-like) colour to the calcification, instead of white (the color of most of the other compounds).
Water hardness is often not expressed as a molar concentration, but rather in various units, such as degrees of general hardness (dGH), German degrees (°dH), parts per million (ppm, mg/L, or American degrees), grains per gallon (gpg), English degrees (°e, e, or °Clark), or French degrees (°fH, °F or °HF; lowercase f is used to prevent confusion with degrees Fahrenheit). The table below shows conversion factors between the various units.
Hardness unit conversion.
mmol/L
ppm, mg/L
dGH, °dH
gpg
°e, °Clark
°fH
mmol/L
1 0.009991 0.1783 0.171 0.1424 0.09991
ppm, mg/L
100.1 1 17.85 17.12 14.25 10
dGH, °dH
5.608 0.05603 1 0.9591 0.7986 0.5603
gpg
5.847 0.05842 1.043 1 0.8327 0.5842
°e, °Clark
7.022 0.07016 1.252 1.201 1 0.7016
°fH
10.01 0.1 1.785 1.712 1.425 1
The various alternative units represent an equivalent mass of calcium oxide (CaO) or calcium carbonate (CaCO3) that, when dissolved in a unit volume of pure water, would result in the same total molar concentration of Mg2+ and Ca2+. The different conversion factors arise from the fact that equivalent masses of calcium oxide and calcium carbonates differ, and that different mass and volume units are used. The units are as follows:
Parts per million (ppm) is usually defined as 1 mg/L CaCO3 (the definition used below).[19] It is equivalent to mg/L without chemical compound specified, and to American degree.
Grains per Gallon (gpg) is defined as 1 grain (64.8 mg) of calcium carbonate per U.S. gallon (3.79 litres), or 17.118 ppm.
a mmol/L is equivalent to 100.09 mg/L CaCO3 or 40.08 mg/L Ca2+.
A degree of General Hardness (dGH or 'German degree (°dH, deutsche Härte))' is defined as 10 mg/L CaO or 17.848 ppm.
A Clark degree (°Clark) or English degrees (°e or e) is defined as one grain (64.8 mg) of CaCO3 per Imperial gallon (4.55 litres) of water, equivalent to 14.254 ppm.
A French degree (°fH or °f) is defined as 10 mg/L CaCO3, equivalent to 10 ppm.
Hard/soft classification[edit]
Because it is the precise mixture of minerals dissolved in the water, together with the water's pH and temperature, that determine the behavior of the hardness, a single-number scale does not adequately describe hardness. However, the United States Geological Survey uses the following classification into hard and soft water,[20]
Classification
hardness in mg/L
hardness in mmol/L
hardness in dGH/°dH
hardness in gpg
hardness in ppm
Soft 0–60 0–0.60 0-3.37 0-3.50 less than 60
Moderately hard 61–120 0.61–1.20 3.38-6.74 3.56-7.01 60-120
Hard 121–180 1.21–1.80 6.75–10.11 7.06-10.51 120-180
Very hard ≥ 181 ≥ 1.81 ≥ 10.12 ≥ 10.57 > 181
Seawater is considered to be very hard due to various dissolved salts. Typically seawater's hardness is in the range of 6630 ppm. In contrast, freshwater has hardness in the range of 15 - 375 ppm.[21]
Indices[edit]
Several indices are used to describe the behaviour of calcium carbonate in water, oil, or gas mixtures.[22]
Langelier saturation index (LSI)[edit]
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The Langelier saturation index (sometimes Langelier stability index) is a calculated number used to predict the calcium carbonate stability of water. It indicates whether the water will precipitate, dissolve, or be in equilibrium with calcium carbonate. In 1936, Wilfred Langelier developed a method for predicting the pH at which water is saturated in calcium carbonate (called pHs). The LSI is expressed as the difference between the actual system pH and the saturation pH:
LSI = pH (measured) − pHs
For LSI > 0, water is super saturated and tends to precipitate a scale layer of CaCO3.
For LSI = 0, water is saturated (in equilibrium) with CaCO3. A scale layer of CaCO3 is neither precipitated nor dissolved.
For LSI < 0, water is under saturated and tends to dissolve solid CaCO3.
If the actual pH of the water is below the calculated saturation pH, the LSI is negative and the water has a very limited scaling potential. If the actual pH exceeds pHs, the LSI is positive, and being supersaturated with CaCO3, the water has a tendency to form scale. At increasing positive index values, the scaling potential increases.
In practice, water with an LSI between -0.5 and +0.5 will not display enhanced mineral dissolving or scale forming properties. Water with an LSI below -0.5 tends to exhibit noticeably increased dissolving abilities while water with an LSI above +0.5 tends to exhibit noticeably increased scale forming properties.
The LSI is temperature sensitive. The LSI becomes more positive as the water temperature increases. This has particular implications in situations where well water is used. The temperature of the water when it first exits the well is often significantly lower than the temperature inside the building served by the well or at the laboratory where the LSI measurement is made. This increase in temperature can cause scaling, especially in cases such as hot water heaters. Conversely, systems that reduce water temperature will have less scaling.
Water Analysis:
pH = 7.5
TDS = 320 mg/L
Calcium = 150 mg/L (or ppm) as CaCO3
Alkalinity = 34 mg/L (or ppm) as CaCO3
LSI Formula:
LSI = pH - pHs
pHs = (9.3 + A + B) - (C + D) where:
A = (Log10[TDS] - 1)/10 = 0.15
B = -13.12 x Log10(°C + 273) + 34.55 = 2.09 at 25 °C and 1.09 at 82 °C
C = Log10[Ca2+ as CaCO3] - 0.4 = 1.78
(Ca2+ as CaCO3 is also called Calcium Hardness and is calculated as=2.5(Ca2+))
D = Log10[alkalinity as CaCO3] = 1.53
Ryznar Stability Index (RSI)[edit]
The Ryznar stability index (RSI) uses a database of scale thickness measurements in municipal water systems to predict the effect of water chemistry.
Ryznar saturation index (RSI) was developed from empirical observations of corrosion rates and film formation in steel mains. It is defined as:
RSI = 2 pHs – pH (measured)
For 6,5 < RSI < 7 water is considered to be approximately at saturation equilibrium with calcium carbonate
For RSI > 8 water is under saturated and, therefore, would tend to dissolve any existing solid CaCO3
For RSI < 6,5 water tends to be scale forming
Puckorius Scaling Index (PSI)[edit]
The Puckorius Scaling Index (PSI) uses slightly different parameters to quantify the relationship between the saturation state of the water and the amount of limescale deposited.
Other indices[edit]
Other indices include the Larson-Skold Index,[23] the Stiff-Davis Index,[24] and the Oddo-Tomson Index.[25]
Regional information[edit]
The hardness of local water supplies depends on the source of water. Water in streams flowing over volcanic (igneous) rocks will be soft, while water from boreholes drilled into porous rock is normally very hard.
In Australia[edit]
Analysis of water hardness in major Australian cities by the Australian Water Association shows a range from very soft (Melbourne) to hard (Adelaide). Total Hardness levels of calcium carbonate in ppm are: Canberra: 40;[26] Melbourne: 10–26;[27] Sydney: 39.4–60.1;[28] Perth: 29–226;[29] Brisbane: 100;[30] Adelaide: 134–148;[31] Hobart: 5.8–34.4;[32] Darwin: 31.[33]
In Canada[edit]
Prairie provinces (mainly Saskatchewan and Manitoba) contain high quantities of calcium and magnesium, often as dolomite, which are readily soluble in the groundwater that contains high concentrations of trapped carbon dioxide from the last glaciation. In these parts of Canada, the total hardness in ppm of calcium carbonate equivalent frequently exceed 200 ppm, if groundwater is the only source of potable water. The west coast, by contrast, has unusually soft water, derived mainly from mountain lakes fed by glaciers and snowmelt.
Some typical values are: Montreal 116 ppm,[34] Calgary 165 ppm, Regina 496 ppm,[35] Saskatoon 160-180 ppm,[36] Winnipeg 77 ppm,[37] Toronto 121 ppm,[38] Vancouver < 3 ppm,[39] Charlottetown, PEI 140–150 ppm,[40] Waterloo Region 400 ppm, Guelph 460 ppm,[41] Saint John (West) 160-200 ppm.[42]
In England and Wales[edit]
Hardness water level of major cities in the UK
Area
Primary source
Level[43]
Manchester Lake District (Haweswater, Thirlmere) Pennines (Longdendale Chain) 1.750 °clark / 25 ppm[44]
Birmingham Elan Valley Reservoirs 3 °clark /
42.8 ppm[45]
Bristol Mendip Hills (Bristol Reservoirs) 16 °clark / 228.5 ppm[46]
Southampton Bewl Water 18.76 °clark / 268 ppm[47]
London (EC1A) Lee Valley Reservoir Chain 19.3 °clark / 275 ppm[48]
Information from the British Drinking Water Inspectorate[49] shows that drinking water in England is generally considered to be 'very hard', with most areas of England, particularly east of a line between the Severn and Tees estuaries, exhibiting above 200 ppm for the calcium carbonate equivalent. Water in London, for example, is mostly obtained from the River Thames and River Lea both of which derive significant proportion of their dry weather flow from springs in limestone and chalk aquifers. Wales, Devon, Cornwall and parts of North-West England are softer water areas, and range from 0 to 200 ppm.[50] In the brewing industry in England and Wales, water is often deliberately hardened with gypsum in the process of Burtonisation.
Generally water is mostly hard in urban areas of England where soft water sources are unavailable. A number of cities built water supply sources in the 18th century as the industrial revolution and urban population burgeoned. Manchester was a notable such city in North West England and its wealthy corporation built a number of reservoirs at Thirlmere and Haweswater in the Lake District to the north. There is no exposure to limestone or chalk in their headwaters and consequently the water quality in Manchester is rated as 'very soft'.[44] Similarly, tap water in Birmingham is also soft as it is sourced from the Elan Valley Reservoirs in Wales.
In Ireland[edit]
The EPA has published a standards handbook for the interpretation of water quality in Ireland in which definitions of water hardness are given.[51] In this section, reference to original EU documentation is given, which sets out no limit for hardness. In turn, the handbook also gives no "Recommended or Mandatory Limit Values" for Hardness. The handbooks does indicate that above the midpoint of the ranges defined as "Moderately Hard", effects are seen increasingly: "The chief disadvantages of hard waters are that they neutralise the lathering power of soap.... and, more important, that they can cause blockage of pipes and severely reduced boiler efficiency because of scale formation. These effects will increase as the hardness rises to and beyond 200 mg/l CaCO3."
In the United States[edit]
A collection of data from the United States found that about half the water stations tested had hardness over 120 mg per litre of calcium carbonate equivalent, placing them in the categories "hard" or "very hard".[20] The other half were classified as soft or moderately hard. More than 85% of American homes have hard water.[52] The softest waters occur in parts of the New England, South Atlantic-Gulf, Pacific Northwest, and Hawaii regions. Moderately hard waters are common in many of the rivers of the Tennessee, Great Lakes, and Alaska regions. Hard and very hard waters are found in some of the streams in most of the regions throughout the country. The hardest waters (greater than 1,000 ppm) are in streams in Texas, New Mexico, Kansas, Arizona, and southern California.[53]
See also[edit]
Water portal
Carbonate hardness
dGH
Water softener
Water quality
Water treatment
Water purification
References[edit]
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External links[edit]
"Langelier Saturation Index (LSI) Calculato". Akzo Nobel. Retrieved 29 August 2017.
"Water hardness unit converter". Retrieved 29 August 2017.
"UK Hard Water Map". Retrieved 2 December 2017.
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Agonist-antagonist
From Wikipedia, the free encyclopedia
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In pharmacology the term agonist-antagonist or mixed agonist/antagonist is used to refer to a drug which under some conditions behaves as an agonist (a substance that fully activates the receptor that it binds to) while under other conditions, behaves as an antagonist (a substance that binds to a receptor but does not activate and can block the activity of other agonists).
Types of mixed agonist/antagonist include receptor ligands that act as agonist for some receptor types and antagonist for others[1] or agonist in some tissues while antagonist in others (also known as selective receptor modulators).
Agonist-antagonist opioids[edit]
The best known agonist-antagonists are opioids. Examples of such opioids are:
pentazocine, agonist at the kappa (κ) and sigma (σ) and has a weak antagonist action at the mu opioid receptor (μ).[2]
butorphanol, partial agonist at μ- and a pure agonist at κ-opioid receptor and antagonist activity at the delta opioid receptor (δ)[3]
nalbuphine, κ-agonist/μ-antagonist analgesic[4]
Agonist–antagonist opioids usually have a ceiling effect – over particular dose they don't increase their potency.[5] Hence agonist–antagonist opioids have a lower addiction potential but also lower analgesic efficacy and are more likely to produce psychotomimetic effects.[6]
Agonist–antagonist opioids that block delta while activating mu opioid receptors produce analgesia without the development of tolerance.[7]
See also[edit]
Partial agonist
Competitive antagonist
Inverse agonist
References[edit]
Jump up ^ Hoskin PJ, Hanks GW (1991). "Opioid agonist-antagonist drugs in acute and chronic pain states". Drugs. 41 (3): 326–44. doi:10.2165/00003495-199141030-00002. PMID 1711441.
Jump up ^ Hollister LE (17 July 1991). "AMA Drug Evaluations Annual 1991". JAMA: The Journal of the American Medical Association. 266 (3): 97. doi:10.1001/jama.1991.03470030126039.
Jump up ^ Commiskey S, Fan LW, Ho IK, Rockhold RW (2005). "Butorphanol: effects of a prototypical agonist-antagonist analgesic on kappa-opioid receptors". Journal of Pharmacological Sciences. 98 (2): 109–16. doi:10.1254/jphs.CRJ05001X. PMID 15942128.
Jump up ^ Schmidt WK, Tam SW, Shotzberger GS, Smith DH, Clark R, Vernier VG (1985). "Nalbuphine". Drug and Alcohol Dependence. 14 (3-4): 339–62. doi:10.1016/0376-8716(85)90066-3. PMID 2986929.
Jump up ^ Benson GJ, Tranquilli WJ (1992). "Advantages and guidelines for using opioid agonist-antagonist analgesics". Veterinary Clinics of North America: Small Animal Practice. 22 (2): 363–5. doi:10.1016/S0195-5616(92)50637-4. PMID 1585578.
Jump up ^ Lasagna L (1987). "Benefit-risk ratio of agonist-antagonist analgesics". Drug and Alcohol Dependence. 20 (4): 385–93. doi:10.1111/j.1360-0443.1989.tb00595.x. PMID 2894291.
Jump up ^ Dietis N, Guerrini R, Calo G, Salvadori S, Rowbotham DJ, Lambert DG (2009). "Simultaneous targeting of multiple opioid receptors: a strategy to improve side-effect profile". British Journal of Anaesthesia. 103 (1): 38–49. doi:10.1093/bja/aep129. PMID 19474215.
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Japanese pagoda
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Multi-storied pagodas in wood and stone, and a gorintō
Pagodas in Japan are called tō (塔, lit. pagoda), sometimes buttō (仏塔, lit. Buddhist pagoda) or tōba (塔婆, lit. pagoda) and historically derive from the Chinese pagoda, itself an interpretation of the Indian stupa.[1] Like the stupa, pagodas were originally used as reliquaries but in many cases they ended up losing this function.[2] Pagodas are quintessentially Buddhist and an important component of Japanese Buddhist temple compounds but, because until the Kami and Buddhas Separation Act of 1868, a Shinto shrine was normally also a Buddhist temple and vice versa, they are not rare at shrines either. The famous Itsukushima Shrine, for example, has one.[3]
After the Meiji Restoration the word tō, once used exclusively in a religious context, came to mean also "tower" in the western sense, as for example in Eiffel tower (エッフェル塔, Efferu-tō).
Of the Japanese pagoda's many forms, some are built in wood and are collectively known as mokutō (木塔, lit. wood pagoda), but most are carved out of stone (sekitō (石塔, lit. stone pagoda). Wood pagodas are large buildings with either two stories (like the tahōtō (多宝塔, lit. Tahō pagoda), see photo below) or an odd number of stories. Extant wood pagodas with more than two storeys have almost always either three storeys (and are therefore called sanjū-no-tō (三重塔, lit. three-storeyed pagoda)) or five (and are called gojū-no-tō (五重塔, lit. five-storeyed pagoda). Stone pagodas are nearly always small, usually well below 3 metres, and as a rule offer no usable space. If they have more than one storey, pagodas are called tasōtō (多層塔, lit. multi-storied pagoda) or tajūtō (多重塔, lit. multi-storied pagoda).
A pagoda's size is measured in ken, where a ken is the interval between two pillars of a traditional-style building. A tahōtō for example can be either 5x5 ken or 3x3 ken.[4] The word is usually translated in English as "bay" and is better understood as an indication of proportions than as a unit of measurement.
Contents
[hide]
1 History
1.1 Design and structure evolution
1.2 Loss of importance of the pagoda within the garan
2 Stone pagodas
2.1 Tasōtō or tajūtō
2.2 Hōtō
2.3 Gorintō
2.4 Hōkyōintō
2.5 Muhōtō or rantō
2.6 Kasatōba
2.7 Sōrintō
3 Wooden pagodas
3.1 Tasōtō
3.2 Hōtō
3.3 Tahōtō
3.3.1 Daitō
3.4 Sotōba
4 Gallery of pagodas in Japan
5 See also
6 Notes
7 References
8 Bibliography
History[edit]
Japan's oldest three-storeyed pagoda at Hokki-ji, Ikaruga, Nara Pref. It was built in 706.
The stupa was originally a simple mound containing the Buddha's ashes which in time became more elaborate, while its finial grew proportionally larger.[2] After reaching China, the stupa met the Chinese watchtower and evolved into the pagoda, a tower with an odd number of storeys.[note 1] Its use then spread to Korea and, from there, to Japan. Following its arrival in Japan together with Buddhism in the 6th century, the pagoda became one of the focal points of the early Japanese garan.[note 2] In Japan it evolved in shape, size and function, finally losing its original role as a reliquary.[5] It also became extremely common, while on the Asian continent it is rare.[6]
With the birth of new sects in later centuries, the pagoda lost importance and was consequently relegated to the margins of the garan. Temples of the Jōdo sects rarely have a pagoda.[2] During the Kamakura period the Zen sect arrived in Japan and their temples do not normally include a pagoda.
Pagodas originally were reliquaries and did not contain sacred images, but in Japan many, for example Hōryū-ji's five-storied pagoda, enshrine statues of various deities.[5] To allow the opening of a room at the ground floor and therefore create some usable space, the pagoda's central shaft, which originally reached the ground, was shortened to the upper stories, where it rested on supporting beams.[5] In that room are enshrined statues of the temple's main objects of worship. Inside Shingon pagodas there can be paintings of deities called Shingon Hasso (真言八祖); on the ceiling and on the central shaft there can be decorations and paintings.[5]
Design and structure evolution[edit]
The edge of a pagoda's eaves forms a straight line, with each following edge being shorter than the other. The more difference in length (a parameter called teigen (逓減, gradual diminution) in Japanese) between stories, the more solid and secure the pagoda seems to be. Both teigen and the finial are greater in older pagodas, giving them a sense of solidity.[5] Vice versa, recent pagodas tend to be steeper and have shorter finials, creating svelter silhouettes.
From the structural point of view, old pagodas had a stone base (心礎, shinso) over which stood the main pillar (心柱, shinbashira). Around it would be erected the first story's supporting pillars, then the beams supporting the eaves and so on. The other stories would be built over the completed one, and on top of the main pillar would at last be inserted the finial.[5] In later eras, all of the supporting structures would be erected at once, and later to them were fixed parts of more cosmetic function.[5]
Early pagodas had a central pillar that penetrated deep into the ground. With the evolution of architectural techniques, it was first put to rest on a base stone at ground level, then it was shortened and put to rest on beams at the second story to allow the opening of a room.[2][5]
Their role within the temple declined gradually while they were being functionally replaced by main halls (kondō). Originally the centerpiece of the Shingon and Tendai garan, they were moved later to its edges and finally abandoned, in particular by the Zen sects, the last to appear in Japan.
Loss of importance of the pagoda within the garan[edit]
A reconstruction of Asuka-dera's original layout with a pagoda at its center
Because of the relics they contained, wooden pagodas used to be the centerpiece of the garan, the seven edifices considered indispensable for a temple.[7] They gradually lost importance and were replaced by the kondō (golden hall), because of the magic powers believed to lie within the images the building housed. This loss of status was so complete that Zen schools, which arrived late in Japan from China, normally do not have any pagoda in their garan. The layout of four early temples clearly illustrates this trend: they are in chronological order Asuka-dera, Shitennō-ji, Hōryū-ji, and Yakushi-ji.[7] In the first, the pagoda was at the very center of the garan surrounded by three small kondō (see the reconstruction of the temple's original layout). In the second, a single kondō is at the center of the temple and the pagoda lies in front of it. At Hōryū-ji, they are one next to the other. Yakushi-ji has a single, large kondō at the center with two pagodas on the sides. The same evolution can be observed in Buddhist temples in China.
Stone pagodas[edit]
A rare 16-story stone pagoda at Chōshō-ji in Kamakura
Stone pagodas (sekitō) are usually made of materials like apatite or granite, are much smaller than wooden ones and are finely carved.[5] Often they bear sanskrit inscriptions, Buddhist figurines and Japanese lunar calendar dates nengō. Like wooden ones, they are mostly classifiable on the basis of the number of stories as tasōtō or hōtō, but there are however some styles hardly ever seen in wood, namely the gorintō, the muhōtō, the hōkyōintō and the kasatōba.[8]
Tasōtō or tajūtō[edit]
With a few very rare exceptions, tasōtō (also called tajūtō) have an odd number of stories, normally comprised between three and thirteen.[9] They are usually less than three meters tall, but they can occasionally be much taller. The tallest still extant is a 13-story pagoda at Hannya-ji in Nara, which is 14.12 m. They are often dedicated to Buddha and offer no usable room, but some have a small space inside which holds a sacred image.[8] In the oldest extant specimen, while the edge of each story are parallel to the ground, each successive story is smaller than the next, resulting in a strongly slanted curve. More modern tasōtō tend to have a less pronounced curve.
Media related to tasōtō at Wikimedia Commons
Hōtō[edit]
A hōtō at Ankokuron-ji
A hōtō (宝塔, lit. jewel stupa) is a pagoda consisting of four parts: a low foundation stone, a cylindrical body with a rounded top, a four-sided roof and a finial.[10] Unlike the similar tahōtō (see section below) it has no enclosed pent roof (mokoshi) around its circular core.[5] Like the tahōtō it takes its name from Buddhist deity Tahō Nyorai. The hōtō was born during the early Heian period, when the Tendai and Shingon sects first arrived in Japan. Indeed, because it does not exist on the Asian continent, it is believed to have been invented in Japan.[5]
There used to exist full-size hōtō, but almost only miniature ones survive, normally made of stone and/or metal.[10]
Media related to hōtō at Wikimedia Commons
Gorintō[edit]
Main article: Gorintō
A gorintō
The gorintō (五輪塔, lit. five ring tower) is a pagoda found almost only in Japan and believed to have been first adopted by the Shingon and Tendai sects during the mid Heian period.[11] It is used as a tomb marker or as a cenotaph, and is therefore a common sight in Buddhist temples and cemeteries. It is also called gorinsotōba (五輪卒塔婆) ("five-ringed stupa") or goringedatsu (五輪解脱), where the term sotoba is a transliteration of the Sanskrit word stupa.[1]
In all its variations, the gorintō is made of five blocks (although that number can sometimes be difficult to detect), each having one of the five shapes which symbolize of the Five Elements believed to be the basic building blocks of reality: earth (cube), water (sphere), fire (pyramid), air (crescent), and ether, energy, or void (lotus).[11] The last two rings (air and ether) are visually and conceptually united into a single subgroup.
Media related to gorintō at Wikimedia Commons
Hōkyōintō[edit]
Main article: Hōkyōintō
A hōkyōintō
The hōkyōintō (宝篋印塔) is a large stone pagoda so called because it originally contained the Hōkyōin (宝篋印) dharani (陀羅尼) sūtra.[1] It was originally used as a cenotaph for the King of Wuyue - Qian Liu in China.[1]
The hōkyōintō tradition in Japan is believed to have begun during the Asuka period (550–710 CE).[12] They used to be made of wood and started to be made in stone only during the Kamakura period.[12] It is also during this period that they started to be used as tombstones and cenotaphs.[12] The hōkyōintō started to be made in its present form during the Kamakura period.[1] Like a gorintō, it is divided in five main sections representing the five elements of Japanese cosmology.[5] The sūtra it sometimes hides contain all the pious deeds of a Tathagata Buddha, and the faithful believe that, by praying in front of the hōkyōintō, their sins will be canceled, during their lives they will be protected from disasters and after death they will go to heaven.[12]
Media related to hōkyōintō at Wikimedia Commons
Muhōtō or rantō[edit]
A muhōtō
The muhōtō (無縫塔, lit. no stitch tower) or rantō (卵塔, lit. egg tower) is a pagoda which usually marks the gravesite of a Buddhist priest. It was originally used by just the Zen schools, but it was later adopted by the others too.[13] Its characteristic egg-shaped upper portion is supposed to be a phallic symbol.
Media related to muhōtō at Wikimedia Commons
Kasatōba[edit]
A kasatōba (笠塔婆, umbrella stupa) (see photo in the gallery below) is simply a square stone post placed over a square base and covered by a pyramidal roof. Over the roof stand a bowl-shaped stone and a lotus-shaped stone. The shaft can be carved with Sanskrit words or low-relief images of Buddhist gods. Within the shaft there can be stone wheels which allow the faithful to turn the stupa around while praying as with a prayer wheel.[14]
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Sōrintō[edit]
The sōrintō (相輪橖) is a type of small pagoda consisting just of a pole and a sōrin.
Wooden pagodas[edit]
Tasōtō[edit]
Yakushi-ji's Eastern Pagoda
Wooden tasōtō are pagodas with an odd number of stories. Some may appear to have an even number because of the presence between stories of purely decorative enclosed pent roofs called mokoshi[note 3] A famous example is Yakushi-ji's eastern pagoda (see photo to the left), which seems to have six stories but has in fact only three. Another is the tahōtō (see below), which has a single story, plus a mokoshi under its roof, and seems therefore to have two stories.[note 4] There existed specimen with seven or nine stories, but all extant ones have either three (and are therefore called sanjū-no-tō (三重塔, lit. three-storied pagoda)) or five (and are called gojū-no-tō (五重塔, lit. five-storied pagoda).[5]（Tanzan Jinja in Sakurai, Nara, has a pagoda having thirteen, which however for structural reasons is classified separately, and is not considered a tasōtō.)[5] The oldest three-storied pagoda stands at Nara's Hokki-ji and was built between 685 and 706.[5] The oldest extant five-storied pagoda belongs to Hōryū-ji and was built some time during the Asuka period (538 -710). The tallest wooden tasōtō belongs to Tō-ji, Kyoto. It has five stories and is 54 m tall.
Media related to tasōtō at Wikimedia Commons
Hōtō[edit]
A hōtō at Yakuō-ji, Tokushima prefecture
A wooden hōtō is a rare type of pagoda consisting of four parts: a low foundation stone, a cylindrical body with a rounded top, a pyramidal roof and a finial.[10] Unlike the similar tahōtō (see section below) it has no square enclosed pent roof (mokoshi) around its cylindrical core.[5] Like the tahōtō it takes its name from Buddhist deity Tahō Nyorai. The hōtō was born during the early Heian period, when the Tendai and Shingon Buddhist sects first arrived in Japan.
There used to be many full-size hōtō, but almost only miniature ones survive, normally made of stone and/or metal. A good example of full-size hōtō can be seen at Ikegami Honmon-ji in Nishi-magome, Tokyo. The pagoda is 17.4 meter tall and 5.7 meter wide.[10]
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Tahōtō[edit]
Main article: Tahōtō
Negoro-ji's daitō
The tahōtō is a type of wooden pagoda unique for having an even number of stories (two), the first square with a rounded core, the second circular. This style of tō was created surrounding the cylindrical base of a hōtō (see above) with a square, roofed corridor called mokoshi.[note 5][5] The core of the pagoda has just one story with its ceiling below the circular second story, which is inaccessible. Like the tasōtō and the rōmon, in spite of its appearance it therefore offers usable space only at the ground floor.[5]
Because its kind does not exist either in Korea or in China, it is believed to have been invented in Japan during the Heian period (794 - 1185). The tahōtō was important enough to be considered one of the seven indispensable buildings (the so-called shichidō garan) of a Shingon temple.[15] Kūkai himself is responsible for the construction of the tahōto at Mount Kōya's Kongōbu-ji.
Daitō[edit]
The floorplan of Negoro-ji's daitō
Usually the base of a tahōtō is 3-ken across with four main, supporting pillars called shitenbashira (四天柱) at the corners (see drawing).[5] The room the shitenbashira form houses a sanctuary where the main objects of worship (the gohonzon) are enshrined.
Larger, 5x5 ken tahōtō however exist and are called daitō (大塔, lit. large pagoda) because of their dimensions. This is the only type of tahōtō to retain the original structure with a wall separating the corridor (mokoshi) from the core of the structure. This type of pagoda used to be common but, of all daitō ever built, only three are still extant. One is at Wakayama prefecture's Negoro-ji, another at Kongōbu-ji, again in Wakayama, and the last at Kirihata-dera, Tokushima prefecture.[15] The daitō at Kongōbu-ji was founded by Shingon sect's Kūkai. The specimen found at Negoro-ji (see photo above) is 30.85 meters tall and a National Treasure.
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Sotōba[edit]
Often offertory strips of wood with five subdivisions and covered with elaborate inscriptions called sotōba (卒塔婆) can be found at tombs in Japanese cemeteries (see photo in the gallery below).[5] The inscriptions contain sūtra and the posthumous name of the dead person. Their name derives from the Sanskrit stūpa, and they can be also considered pagodas.
Media related to Sotōba at Wikimedia Commons
Gallery of pagodas in Japan[edit]
A gorintō
A hōkyōintō
A hōtō
A stone tasōtō
Two kasatōba at Hannya-ji, Nara
Ichijō-ji's sanjū-no-tō (three storied pagoda). It was built in 1171.
Murō-ji's gojū-no-tō (five storied pagoda). It was built in 800.
A pagoda at a Shinto shrine, Itsukushima Shrine
A sotōba. Clearly visible is the division in five sections
A sorintō
See also[edit]
Shinbashira, the suspended wooden column inside.
Notes[edit]
Jump up ^ Odd numbers are strongly favoured by Chinese numerology and Buddhism. They are supposed to represent yang, that is, the male and positive principle, and are therefore considered lucky.
Jump up ^ Temple compound, ideally composed of seven buildings.
Jump up ^ Besides being decorative in themselves,they are also used also to hide structural components which would otherwise mar the pagoda's feel.
Jump up ^ On the subject, see also the articles Hisashi, Mokoshi and Moya.
Jump up ^ For reasons of space, however, the wall separating the mokoshi from the core of the pagoda is present only in large tahōtō called daitō (see the next section).
References[edit]
^ Jump up to: a b c d e Iwanami Kōjien Japanese dictionary
^ Jump up to: a b c d Jaanus, Tou
Jump up ^ Hamashima, Masashi (1999). Jisha Kenchiku no Kanshō Kiso Chishiki (in Japanese). Tokyo: Shibundō. p. 88.
Jump up ^ Fujita Masaya, Koga Shūsaku, ed. (April 10, 1990). Nihon Kenchiku-shi (in Japanese) (September 30, 2008 ed.). Shōwa-dō. p. 79. ISBN 4-8122-9805-9.
^ Jump up to: a b c d e f g h i j k l m n o p q r s t Fujita & Koga 2008, pp. 79–81
Jump up ^ Scheid, Japanische Pagoden
^ Jump up to: a b * Tamura, Yoshiro (2000). Japanese Buddhism - A Cultural History (First ed.). Tokyo: Kosei Publishing Company. pp. 40–41 pages. ISBN 4-333-01684-3.
^ Jump up to: a b JAANUS, Sekitou
Jump up ^ JAANUS, Tasoutou
^ Jump up to: a b c d JAANUS, Houtou
^ Jump up to: a b JAANUS - Gorintou
^ Jump up to: a b c d Yatsushiro Municipal Museum
Jump up ^ JAANUS - Muhoutou
Jump up ^ JAANUS - Kasatouba
^ Jump up to: a b JAANUS, Daitou
Bibliography[edit]
Iwanami Kōjien (広辞苑) Japanese dictionary, 6th Edition (2008), DVD version
"JAANUS". Japanese Architecture and Art Net Users System. Retrieved 19 August 2010.
Fujita Masaya, Koga Shūsaku, ed. (April 10, 1990). Nihon Kenchiku-shi (in Japanese) (September 30, 2008 ed.). Shōwa-dō. ISBN 4-8122-9805-9.
Scheid, Bernhard. "Japanische Pagoden" (in German). University of Vienna. Retrieved 19 August 2010.
Shinkō no Katachi - Hōkyōintō, Yatsushiro Municipal Museum, accessed on September 18, 2008 (in Japanese)
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