tf6 Qaaltiies and Falue of Fijh Soap. 



Having thus Hated the refults of the experiments laid before the Board of Triiflces by my 

 fether, I will conclude this paper, with feme mifcellaneous obfervations upon the combination 

 of fifli and potaih, and the relation of a few experiments on other faponaceous compounds. 



When cauftic potafli and filh are heated together, a decoaipoiition of the animal matter 

 foon commences, as is dcmonftrated by the feparation of a quantity of ammonia. The 

 quantity of ammoniai feparated or formed in this procefs is fo great, that fliould the fifhy 

 com.pound prove of any ufe, it would be economical to colle£l the ammoniacal vapours in 

 a chamber with muriatic acid gas, to form muriate of ammoniac. This ammonia is deriTed 

 not only from the gelatine, but alfo from the pure fibrous matter, as I found, by particular 

 trials with it. This fllh (bap has a more or lefs brown colour, varies- in its confiftence,. 

 which depends on the quantity of v/ater it contains ; it has a moft difagreeable fmell, and 

 by keeping in a damp place becomes fofter, and acquirss a thin whitifli covering. The bony 

 matter of the fifli is not diffolved, but remains fufpended in. the foap ; fo that when the 

 foap is diflblved in water, the bony matter falls down. When an acid is added, the filhjr 

 matter is feparated of a white colour, and remains diffufcd through the water, giving it a milky 

 appearance. 



Sir John Dalrymple mentions in his printed letters, that from repeated experience, he 

 has diicovered this foap to be polTefled of peculiar properties, which he fays, independent of its 

 cheapnefs, will render it an object of great national concern. The following experiments were 

 made to try the truth of Sir John Dalrymple's ftatements,as alfo to obferve if this compound 

 bad fimilar properties wit"h common foap. 



1. With diflilled water it forms a brown-coloured folution, which being kept for feven or 

 eight weeks, did not alter in its appearance or fmell. It alfo lathered pretty well. 



2. With foft water it forms a brown-coloured folution, and lathers well. 



3. With hard water it is changed in the fame manner as common foap,. a part of the 

 faponaceous compound being decompofed by the earthy falts, which are generally to be 

 found in fuch kinds of water. Sir John Dalrymple, however, aflerts, that it wafhes equally- 

 well in cold hard, as in cold foft water, and befides, that it waflies with equal advantage. 

 although the water be not heated. The experiment which has been juft mentioned, fliews 

 that it does not differ from common foap when ufed with hard water — that it waflies equally 

 well in cold as in warm water, does not require refutation. 



4. If this foap be agitated in cold fea water, a part of it is decompofed by the earthy falts, 

 contained in the water, and the water acquires a milky appearance. This decompofition is 

 rendered, the more evidfent, if the folution be kept for fome time, for it then acquires a molt- 

 difagreeable fmell, owing to the putrefaction of the animal matter, which had been feparated 

 by means of the earthy falts. Sir John Dalrymple affirms, that this foap waflies well in cold: 

 fea water, which he juftly obferves, is a difcovery of great importance. The milky appear- 

 ance, and' imperfe£t lathering which this foap exhibits when agitated with cold fea water, 

 has- probably led Sir John Dalrymple to draw this conclufion. Thefe appearances, however, 

 are no proof of iis pofleffing any greater cleanfing power than common foap with fait water. 



Accordingly 



