The economy of nature explained and illustrated on the principles of modern philosophy / By G. Gregory.
- George Gregory
- Date:
- 1796
Licence: Public Domain Mark
Credit: The economy of nature explained and illustrated on the principles of modern philosophy / By G. Gregory. Source: Wellcome Collection.
29/632 page 7
![oa ; : Chap. 2.] i Manufatiure of Soap. ' 7 though many fubftances will fufe the vitrifiable earths, and reduce thern toa kind of glafs, the> alkalis are found the moft effectual and convenient. In the foap manufactory alfo the alkalis are a principal and effential ingredient. Common foap is indeed a combination of fixed alkali in a cauttic ftate with fat and oily matters... A very fine fpécies of foap is formed by the union of mineral alkali with olive-oil, or oil of {weet almonds. In the making of this fubftance, the alkali is fir ren-. dered cauftic by boiling it with half its weight of guick-lime, which abftracts its carbonic acid or fix- ed air by fuperior attraction. What is called foap- leys is a folution of the cauftic allcali in water, which is evaporated to fuch a degree of denfity as to be able to fuftain a new-laid egg. To make the finer foap, a part of this lixivium is to be diluted, and mixed with an equal quantity of olive-oil. The mixture 1S put ona gentle fire, and agitated, by which the union 1s ace léeatinl, When the mixture. begins to unite well, the reft of the lixivium is to be ad- ded to it, and the whole is to be digefted with a gentle heat, tll the foap is completely made. Good foap of this kind is white and firm when cold, and is not lable to become moift on expofure to air; itis entirely mifcible with water, to which . it gives a milky appearance, without exhibiting any particles of oil on the furface. | In the making of foft, liquid, green, or black {oaps, cheaper oils are employed, as oil of nuts, of hemp, of fifh, &c. but tallow is the ingredient ufed in our common hard foap. Ba Ol](https://iiif.wellcomecollection.org/image/b33289736_0029.jp2/full/800%2C/0/default.jpg)
