Memoir on the Nature offal Suhtancci. I37 



the smell of burnt woo!, and forms a black spot on the silver 

 ovvmg to the presence of sulubur. ' 



When submitted to distillation, it gave out ammonia and sul- 

 phuretted hydrogen gas, but nuich less than wool, u, short 

 this annual substance contracts no contbination with the alkalie-' 

 wooj"^ ^-^''^' ^" ^^^ ^^te of simple mixture only in the soap of 



Of Saponifcalion, 

 Now that we have examined the results of the. action of the 

 acids and the alkalies on a fot substance, the nature of which is 

 homogeneous it is easy to conjecture what passes in saponifica- 

 [on .a general. When we make an acid or an alkali act on suet 

 the three principles which constitute it, viz. hydrogen, oxvgen' 

 and carbon, which were in a state of equilibrium, L sepamted 

 and combined ni another order to form adip'ocire, and an oil very 

 soluble m alcohol. These two materials are indispensable tJ 



il.n ?. ? ^^ 'r^. "* ^^"^ ^"'''^>'^ ^■^'■'^ ^^ to be noted, tha^ 

 when the fixea oils cto not contain suet in a sensible d-gree the>- 

 cannot produce adipocire during their saponification, and fo-- 



his reason they only furnish soft soaps, like those which we obi 

 tain with pure olive or other vegetable oils, and even with fish 

 on, bu by adding to them a certain quantity of suet, thev pro- 

 duce solid soaps. ' ' '^ 



We may also infer from the foregoing, that most of the oih 

 and suets are not susceptible of uniting immediately with the 

 alkahes, since this union cannot be effected but bv a change o' 

 equilibrium in the elements of tallow or suet or of oil, which be 

 sides requires a prolonged eliullition during a considerable time 

 as the soap-makers very ^^•ell kno,v. It would even be a .ie^ 

 advantage, and save much time and fuel, if by an c^-conomical 

 and specdv method .ve could dispone the fattv substance to unite 

 immediately with the alkalies; hitherto I have found onlv tie 

 concentrated sulphuric acid which can attain this object • i i! 

 sufficient to pour this acid into oil or melted tallow to di'spose 

 them to unite immediately with the alkalies and form a perfect 



ZW ir'Tl ""' '""^'^ "PJ^^^--^ ^« "^^ «« '""^h tlle^nore 

 profitable that the last portions of alkalies, even those which a e 

 combined with the carbonic acid, may enter into combinatfon 

 with the fat matte. ; which is far from being the case in he 

 cojnmon preparation of soap, since the water which passes off 

 still contains alkali, which will not act upon fat. ^ 



Of Rancidity. 

 The results of the rancidity of fat had not vet been well ap- 

 predated, since all chemists have admitted that an acid was 



formed; 



