CHAMBERS'S INFORMATION FOR THE PEOPLE. 



It may also be a question whether, from the 

 better keeping qualities of waters of a moderate 

 degree of hardness, from their general better 

 aeration and greater freshness, and from their 

 less solvent power, such waters are not the best 

 for drinking purposes. Perfectly pure water does 

 not exist in nature. All spring and river waters 

 contain more or less mineral ingredients ; and it is 

 only in limited mountain districts, where hard and 

 non-calcareous rocks prevail, that water is found 

 approaching a nearer standard of purity. That 

 the use of these purer waters is more conducive to 

 health, is without proof; but as far as the mere 

 taste is concerned, there can be no doubt that 

 water of a moderate degree of hardness is much 

 more palatable and agreeable than the mawkish 

 discharge from soft-water districts. The greater 

 power of soft water of dissolving and taking 

 up impurities, such as the colouring matter of 

 peat, is another objection to it. To this may be 

 added its unmistakable action on lead ; which, 

 however, from causes to be afterwards stated, is 

 not so fatal an objection as it at first seems. 

 Putrefactive decomposition appears also to occur 

 less rapidly in hard than in soft waters, and hard 

 water is more easily preserved for a short time in 

 reservoirs and tanks without deterioration. 



With regard to magnesia, its salts are well 

 known to act as powerful medicines when taken 

 in large doses, and, it may be presumed, are not 

 altogether without effect in the small quantities 

 existing in ordinary magnesian waters. A foreign 

 physician has made the observation, that magnesia 

 is the characteristic ingredient of waters in the 

 districts where the diseases called cretinism and 

 goitre abound. 



Of salts of soda and potash, the principal is 

 common salt, or the muriate of soda. Sulphate 

 of soda (Glauber's salt) occurs along with the 

 muriate in the salt-springs of watering-places as 

 well as in the sea-waters. None of ah 1 these salts 

 have any effect on the hardness. In the case of 

 sea-water, which is very hard, the effect is not due 

 to common salt, but to the lime and magnesian 

 salts dissolved in it ; were it not for these, sea- 

 water would be perfectly suitable for washing, 

 although not for drinking. The Artesian-well 

 water of London contains a large amount of alka- 

 line salts, chiefly of soda ; in one case, as much 

 as 42 grains a gallon. Such water is extremely 

 soft for washing purposes, and well adapted for 

 cookery ; but it is doubtful if so great an amount 

 of alkali habitually imbibed be not injurious to the 

 bodily system. 



Salts of iron in considerable quantity make 

 what are technically named chalybeate waters, 

 which belong to the medicinal class. When the 

 iron exists in the spring as carbonate, which is 

 the most usual case, on exposure to the air, it is 

 changed into the peroxide, and falls down in the 

 form of an ochery precipitate. Salts of iron give 

 an inky taste to the water, and a yellowish tint to 

 linen washed in it 



Hardness in Water. 



Hardness in water consists of two kinds, tem- 

 porary and permanent. Perfectly pure or soft 

 water, when exposed to contact with chalk or 

 carbonate of lime, is capable of dissolving only a 

 very minute quantity of that substance, one gallon 



600 



of water, in weight equal to 70,000 grains, taking 

 up no more than two grains of carbonate of lime. 

 This earthy impregnation is said to give the water 

 2 of hardness. But waters are often found con- 

 taining a much larger quantity of carbonate of 

 lime, such as 12, 1 6, or even 20 grains and upwards 

 in the gallon. In such cases, the true solvent of 

 the carbonate of lime, or at least of the excess 

 above 2 grains, is carbonic acid gas, which is 

 1 found to some extent in all natural waters. But 

 ! this gas may be driven off by boiling the water, 

 and the whole carbonate of lime then precipitates 

 in consequence, or falls out of the water, with the 

 exception of the 2 grains, which are held in solu- 

 tion by the water itself. The gas-dissolved car- 

 bonate of lime gives, therefore, temporary hardness, 

 curable by boiling. An artificially prepared hard 

 water, containing 13$ grains of carbonate of lime 

 to the gallon, was observed to decrease from 13-5 

 to 11-2 of hardness merely by heating it in a 

 kettle to the boiling-point. Boiling for 5 minutes 

 reduced the hardness to 6-3, 15 minutes to 4-4, 

 30 minutes to 2-6, and i hour to 2-4. Other salts 

 of lime, such as sulphate of lime, are generally 

 dissolved in water without the intervention of car- 

 bonic acid gas, and therefore remain in solution, 

 although the water is boiled. 



The quality of hardness in water is commonly 

 recognised by the difficulty experienced in wash- 

 ing, and by the amount of soap necessary to form 

 a lather. It occasions an enormous waste of 

 soap, extra labour, and a corresponding tear and 

 wear of clothes. The hardening matter contained 

 in 100 gallons of spring- water, drawn from wells 

 or borings in the chalk strata, will destroy thirty- 

 five ounces of soap that is, the first thirty-five 

 ounces of soap added to this quantity of the water 

 will disappear without forming any lather, or hav- 

 ing any cleansing effect Soap is a compound, 

 formed of an alkali (soda or potash) joined to an 

 oily acid. When a salt of lime, then, is present 

 in the water, the lime decomposes the soap, and 

 combines with the oily acid to form a lime-soap, 

 which is insoluble, and has no detergent pro- 

 perties. 



The most usual hardening ingredients are the 

 salts of lime. Every lime-salt whatsoever hardens 

 water and destroys soap in proportion to the lime 

 present. Salts of magnesia are hardening salts, 

 but not in a regular proportion to the quantity, 

 there being some irregularities in their action. 

 When a magnesia-salt is present along with a 

 lime-salt, the magnesia acts rather as a curdler of 

 the soap than as a destroyer. Salts of iron also 

 produce hardness. Salts of soda and potash have 

 no hardening effect 



The late Dr Clark of Aberdeen devised a scale 

 of hardness which is now generally employed in 

 the chemical description of waters, in which each 

 degree of hardness represents the presence of one 

 grain of carbonate of lime in solution in each 

 gallon. The process consists in the addition of a 

 solution of soap of a certain standard strength to 

 a certain quantity of the water under examination, 

 and the amount necessary to form a lather deter- 

 mines the degree of hardness of the water. 



Next to washing, the deleterious consequences 

 of hardness are felt in various culinary operations, 

 especially in the furring of boilers and cooking 

 utensils, and in the infusion of tea ; and the 

 presence of much sulphate of lime in water makes 



