I^O Compctiiidf ef Oil with jiliali. Lime, an J Ammo/iiac, 



IX. 



^ J\I(i>:s!r on the Comtitiation of Oils ivith Earths., Volatile Alkali, and Metallic Suhjlances. 

 By M. BERTHOLLE-r*. 



^OAP agrees fo far in its properties with neutral f^lts, that oil muft form in the manner 

 of aciils a great numhcr of eon'.binations hitherto neglccled. This notion led me to make 

 the experiments I am about to relate. 



The atlion of oil upon calcareous eartli has long been known ; but Mr. Coftel was the 

 firft who defcribed the method of accurately combining thefe two fubftances, by pouring a 

 folution of foap into lime water +. 



The lime unites to the oil of the foap, and forms a combination which is infoluble, 

 and may be retained on the filter while the caudic alkali is fet at liberty, and may be 

 leparated by evaporation. It retains a fmall quantity of oil, which, according to Mr. Thou- 

 venel, may be wafhcd off with fpirit of wine %. This chemift remarks, in his analyfis of the 

 waters of Contrexeville, that the cauftic alkali cannot decompofe calcareous foap ; fo that 

 we may rigoroudy alhrm, that oil has a llronger affinity to calcareous earth than to fixed 

 alkali ; but according to the fame chcmifts, if the effervefcent fixed alkali be poured on 

 calcareous foap, this lall is decompofed, the alkali unite's with the oil, and the calcareous- 

 earth becomes difengaged at the fame time that it acquires the property of effcrvefcence. 

 The difcoveries made fince this difiertation was written, explain what happens upon this 

 occafion. A double decompofition and recompofition take place. The cretaceous acid 

 unites with the calcareous earth of the oleo-calcareous combination, and the oil of the 

 fame combination unites with the alkali thus deprived of its cretaceous acid. 



M. Thouvenel on this occafion makes a refle£tion of too great importance to be omitted. 

 Phyficians often prefcribe the ufe of foap and lime together, or lime water, without attend- 

 ing to the change and decompofition which refult from the mixture of thefe two fubftances* 

 For, in this cafe, it is the cauftic alkali difengaged from the foap which becomes the aflive 

 medicament ; and confequently that the effefts of fuch mixtures muft; vary according to the 

 proportions and other concomitant circumftances. 



I have likewife examined the effc£ls of volatile alkali upon calcareous foap. The cauftic 

 volatile alkali had no ftronger aftion upon this combination than the cauftic fixed alk;>li ^ 

 but the volatile effervefcent alkali decompofed it in the fiime manner as the effervefcent 

 fixed alkali. The volatile alkali affumed the appearance of an oil, and the earth remained 

 at the bottom in the effervefcent ftate. 



After having decanted this faponaceous fubftancc, I evaporated the fupcrfluous volatile 

 alkali at a gentle heat, and there remained a foap of a more pungent tafte than common foap, 

 and fomewhat lefs confiftent. It became decompofed by long expofure to the air. Spirit 

 of wine diffolves it well, but the quantity taken up by water is extremely fmall. This lad 

 property convinced roe that there was no need of fo' complicated and fo long a procefs tO' 



• Acad. Par. 1780. 



+ Analyfe des Eaux de Pongues. 



t Qu. M. Bcrthollci has fincc Oicwn the cauftic alkali is nlfn folublc in tliat fluid. S'.c . Um I'liilor. Journal, 



