The most important department of domestic economy naturally includes the wash-house, into which philosophy has found its way for the application of many useful principles, and much useful practice. (See 3668.)

655. When Water is Hard, and will not readily unite with soap, it will always be proper to boil it before use; which will be found sufficiently efficacious, if the hardness depends solely upon the impregnation of lime, is the form of what modern chemistry designates as a subcarbonate. The philosophical reason for this is, that the lime, by some secret process of nature, is united to a portion of carbonic acid, which causes it to be suspended in the water: but, in the process of boiling, the carbonic acid unites with the acquired caloric, and is carried off with it into the atmosphere. Even exposure to the atmosphere will produce this effect in a great degree upon spring water so impregnated, leaving it much fitter for lavatory purposes. In both cases the water ought to be carefully poured off from the sediment, as the neutralized lime, when freed from its extra quantity of carbonic acid, falls to the bottom by its own gravity. Boiling, however, has no effect, when the hardness of the water proceeds from lime united with the sulphuric acid, or sulphate of lime of the modern chemistry; and it must be neutralized, or brought to its proper state, by the application of common wood ashes from the kitchen grate, or of barilla, now called soda, or the Dantzic ashes, or pearl-ash: or by the more scientific process of dropping in a solution of subcarbonate of potash. Each of these unite with the sulphuric acid, and separate it from the lime, which gravitates, as in the former case, to the bottom. Having thus philosophically explained the arcana of the washing-tub, we may offer a saving hint in order to economise the use of soap, which is, to put any quantity of pearl-ash into a large jar, covered from the dust; in a few days the alkali will become liquid, which must be diluted in double 'us quantity of soft water with its equal quantity of new-slacked lime. Boil it half-an-hour, frequently stirring it; adding as much more hot water and drawing off the liquor, when the residuum may be boiled afresh, and drained, until it ceases to feel acrid to the tongue.

656. Soap and labour may be saved by dissolving alum and chalk in bran-water, in which the linen ought to be boiled, then well rinsed out, and exposed to the usual process of bleaching.

657. Soap may be disused, or nearly so, in the getting up of muslims and chintzes, which should always be treated agreeably to the oriental manner; that is, to wash them in plain water, and then boil them in congee or rice-water: after which they ought not to be submitted to the operation of the smoothing iron, but rubbed smooth with a polished stone.

658. The economy which must result from these processes renders their consideration important to every private family, in addition to which we must state that the improvements in philosophy extend to the laundry as well as to the wash-house.