The bleacher cannot use with advantage waters impregnated with earthy salts; and a minute portion of iron imparts to the cloth a yellowish hue.
To the manufacturer of painters' colours, water as pure as possible is absolutely essential for the successful preparation of several delicate pigments. Carmine, madder lake, ultramarine, and Indian yellow, cannot be prepared without perfectly pure water.
For the steeping or raiting of flax, soft water is absolutely necessary; in hard water the flax may be immersed for months, till its texture be injured, and still the ligneous matter will not be decomposed, and the fibres properly separated.
In the culinary art, the effects of water more or less pure are likewise obvious. Good and pure water softens the fibres of animal and vegetable matters more readily than such as is called _hard_. Every cook knows that dry or ripe pease, and other farinaceous seeds, cannot _readily_ be boiled soft in hard water; because the farina of the seed is not perfectly soluble in water loaded with earthy salts.
Green esculent vegetable substances are more tender when boiled in soft water than in hard water; although hard water imparts to them a better colour. The effects of hard and soft water may be easily shown in the following manner.
Let two separate portions of tea-leaves be macerated, by precisely the same processes, in circumstances all alike, in similar and separate vessels, the one containing hard and the other soft water, either hot or cold, the infusion made with the soft water will have by far the strongest taste, although it possesses less colour than the infusion made with the hard water. It will strike a more intense black with a solution of sulphate of iron, and afford a more abundant precipitate, with a solution of animal jelly, which at once shews that soft water has extracted more tanning matter, and more gallic acid, from the tea-leaves, than could be obtained from them under like circumstances by means of hard water.
Many animals which are accustomed to drink soft water, refuse hard water. Horses in particular prefer the former. Pigeons refuse hard water when they have been accustomed to soft water.
A good criterion of the purity of water fit for domestic purposes, is its softness. This quality is at once obvious by the touch, if we only wash our hands in it with soap. Good water should be beautifully transparent; a slight opacity indicates extraneous matter. To judge of the perfect transparency of water, a quantity of it should be put into a deep glass vessel, the larger the better, so that we can look down perpendicularly into a considerable mass of the fluid; we may then readily discover the slightest degree of muddiness much better than if the water be viewed through the glass placed between the eye and the light. It should be perfectly colourless, devoid of odour, and its taste soft and agreeable. It should send out air-bubbles when poured from one vessel into another; it should boil pulse soft, and form with soap an uniform opaline fluid, which does not separate after standing for several hours.