VOL. LXXII.] PHILOSOPHICAL TRANSACTIONS. l(3Q 



the same time that it dissolved the fat, combined with its acid ; so that if the oil 

 of the soap could be separated from Segner's salt, he should then immediately 

 get to that stage of the process, to arrive at which had cost him so much time 

 and trouble in exper. 46. Now the separation of the oil appeared to him to be 

 no difficult matter, seeing that soap is readily decompounded by every acid, as 

 well as by some neutral salts; and that when decompounded, the oil might be 

 separated by filtration from the watery fluid, and to the residuum left by the eva- 

 poration of this last, vitriolic acid might be added. Being aware, however, that 

 common soap would not be proper, both because the lixivium with which it is 

 prepared is not pure, and because common salt is added to separate the soap from 

 the water, and in part unites with it, he made a soap for the occasion. 



Exper. 58. With lb. ss. quicklime, lb. j- salt of tartar, and lb. vj. hot water, he 

 prepared a caustic lixivium, which he afterwards strained through a thick linen 

 cloth. Of this lixivium he took a 4th part, diluted it with a little water, and 

 boiled it with lb.j. of suet, until most of the aqueous part being evaporated, the 

 alkali and suet began to unite. The remainder of the lixivium was then added, 

 and the boiling was continued with a gentle heat, the mixture being constantly 

 stirred, until a transparent, and as it were mucilaginous compound was formed, 

 which gelatinized as it became cold, and was exactly like common soap before 

 common salt is added to it. 



Having thus prepared a soap suited to his purpose, his next object was to sepa- 

 rate the oil from the alkali, so as to leave the latter combined with the acid of 

 fat, i. e. under the form of Segner's salt. And this he thought he could effect 

 by means of alum. Accordingly, 



Exper. 59, he dissolved the gelatinous compound obtained in the preceding 

 exper. in water, and added some pulverized alum, which immediately caused the 

 oil to rise up to the surface in a coagulated state. This being skimmed off, some 

 more alum was added; and this was repeated 9 times, till no more oil rose up to 

 the surface.* The filtrated liquor was then evaporated to dryness.-f- 



Exper. 60. It occurred to Dr. C. that alum would be the best chemical agent 

 he could employ, for expelling the acid, unmixed with vitriolic acid, from Segner's 

 salt. Accordingly, to 1 parts of Segner's salt he added 1 part of burnt alum, 

 and subjected the mixture to distillation in a sand bath, with a strong heat. 

 When the distillation was over, he found in the receiver a smoking acid, of the 

 same nature with that which was obtained in exper. 53, and he was therefore 



* The proportions should be as follow: to 10 lb. of the soap-jelly dissolved in water add at dif- 

 ferent times 2:oz. of alum. This mixture being filtrated and evaporated, yields 21^ oz of saline 

 matter, consisting of vitriolated tartar, Segner's salt, and a portion of undecompounded alum. 



+ If this liquor be set by to crystallize, the vitriolated tartar and superabundant alum may for the 

 most part be separated} and the remaining liquor may be afterwards evaporated. 



VOL. XV. Z 



