240

PROOFS OF THE PROPERTIES OP SODA.

a hard consistency. The addition however of a certain quantityof soda, or even muriate of soda will produce the effect of conso-lidating it. The formation of white soap may be shown in thefollowing manner:

Let one part of lime (previously slaked) and two of carbonateof soda be boiled in twelve parts of water for half an hour, filterthe lixivium through a linen cloth (pouring back the fluid uponthe cloth till it passes clear) and evaporate it till its specific gra-vity be about 1.3f5, or which is the same thing, till a phialwhich would contain one ounce of water, will hold an ounceand three eighths of the fluid ; this having been done, soap maybe made by mere mixture of this ley with olive oil, in the pro-portion of one part of the former with two of the latter, in a glassor stone-ware vessel. This mixture being beat up from time totime with a wooden spatula, soon becomes consistent, and if leftto stand for four or five days, it forms a white hard soap.

Remark. ..In large manufactories the ley for making soap ismade no stronger than to float a new laid egg, when the work-men begin to form the mixture. The oil or tallow is first boiledwith a weak ley until the whole is formed into a saponaceouscompound. It is then kept boiling with a stronger ley until itacquires a considerable consistence, and seems to be separatingfrom the fluid below. This separation is a very material part ofthe operation ; and to effect it completely, a quantity of commonsalt is added, the materials are continually boiled for three orfour hours, and then the fire is withdrawn. The soap will nowbe found united at the top of the liquor, or what is called thewaste-ley, which is of no further use, and is therefore drawnoff. The soap is now melted for the last time with a ley, oreven with water, it is then allowed to cool for a short time, andafterwards cast into wooden frames. The last melting is of con-siderable importance, as it gives the soap a compact appearance.

The tallow for making soap is reckoned good if J3cwt. yield aton of white soap.