Chap, a*] Martufafture vf Soap^ 7 



Us carbonic acid or fixed air by fuperior attraction. 

 What is called Ibap-ley is a folution of the cauftic 

 alkali in water, which is evaporated to fuch a* degree 

 of denficy as to be able to fuftain a new-laid egg. To 

 make the finer foap, a part of this ley or lixivium (to 

 fpeak in tt-chnical language) is to be diluted, and 

 mixed with an equal quantity of olive-oil. The mix- 

 ture is put on a gentle fire, and agitated, by which the 

 union is accelerated. When the mixture begins to 

 unite well, the reft of the lixivium is to be added to 

 it, and the whole is to be digefted with a gentle heat, till 

 the foap is completely made. Good foap of this kind 

 ,js white and firm when cold, and is not liable to be- 

 come moid on expofure to air ; it is entirely mifcible 

 with water, to which it gives a milky appearance, with- 

 out exhibiting any particles of oil on the furface. 



In the making of foft, liquid, green, or black foaps, 

 cheaper oils are employed, as oil of nuts, of hemp, of 

 fifh, &c. but tallow is the ingredient ufcd in our com- 

 mon hard foap. 



Oil or fat may be feparated from foap by the addition 

 of an acid, without being much altered in its properties. 

 On this account, waters which contain any acid, either 

 in a difengaged ftate, or combined with any fubftance 

 except fixed alkali, decompofe foap, and will not com- 

 pletely mix with it. 



In this decompofition, efpecially that effected by 

 the vitriols of lime and magnefia, which are frequently 

 contained in water, the vitriolic acid unites with the 

 fixed alkali of the foap, and forms vitriol of fqda, or 

 .Glauber's faltj and the lime or the magnefia combines 

 with the oil, and forms a kind of foap fcarcely at all 

 voluble, which floats in a whitifh curd-like maffes on 

 the furface of the water. 



The VOLATILE alkali or ammonia is fcldom or 

 B 4 never 



