6Z Inquiry into the Laws of Affinity, 



lo. EfSorefcence ought alfo to be confidered as a force whichi in the complex affinities, 

 may determine a combination poflefling this property, and to this is owing the formation of 

 natron in the valley of the Lake of Natron, and other places where the fame circum- 

 ftances occur. 



The obfervations which I have prefented to the Inftitute of Egypt, which will form a 

 fequel to the interefting difcovery of the valley of the Lakes of Natron, for which we are 

 indebted to General Andreoffi, prove that the circumftances neceflary to the formation of 

 natron are, i. a fand, which contains much carbonate of lime ; 2. moifture ; and, 3. the 

 prefence of the muriate of fodf : I have alfo remarked that the ftalks of the reed in a great 

 degree facilitate the produ6lion of this fubftance. I have promifcd to explain the formation 

 of jhe carbonate of foda by means of thefe circumftances, which I ftiall now endeavour 

 to perform. 



Calcareous fand, conftantly impregnated with moifture, may be confidered as a folution 

 of tlie muriate of foda, which a£ls upon the carbonate of lime. Now it follows, from 

 what has been explained in Art. IV. that infolubllity caufes a great diminution in the 

 mutual a£tion of a folid and a liquid fubftance, but that it does not deftroy ir. This a<Sioa 

 is oppofed to the infolubility of the carbonate of lime, which is not abfolute. A folution 

 muft therefore be formed of a fmall quantity of carbonate of lime, and confequently 

 (No. I and 2), the conftituent parts of this carbonate and of the muriate of foda, which 

 are in folution, exert a reciprocal a£tion ; otherwife the prefence of the carbonate of lime 

 would not be, a condition neceffary to the formation of the carbonate of foda*. 



We muft, therefore, confider the humidity of the calcareous fand, in which the c^- 

 bonate of foda is formed, as a folution of muriate of foda and a fmall quantity of carbonate 

 of lime : hence the foda is found in the prefence of the carbonic acid, and the efflorefcence, 

 which is a property of the carbonate of foda, ought to be confidered as a new force that 

 tends to remove it from this combination. In fliort, when, in a foil impregnated with 

 muriate of foda, we meet with the ftalks of reeds which favour the efflorefcence, the car- 

 bonate of foda not only accumulates round thefe ftalks, but fometimes it is not formed 



* The Iblution of the carbonate of lime by the muriate of pot-afli, and by the fulphate of pot-afli, which 

 indubitably a6t like the muriate of foda, has been proved by a direft experiment, for which we are in- 

 debted to Guyton {Mem. de Scbeele, part II. note de la page 18). " The folution of fulpliate of pot-alh, 

 " muriate of pot-alh, &c. poured in lirae water which has been rendered milky by water impregnated with 

 «< carbonic acid gas, immediately caufed the precipitate to difappear. There was likewife no earthy preci- 

 " pitate when water, charged with carbfnic acid gas, was poured in a mixture of lime water and a folution 

 " of thefe neutral falts ; the liquor always contained a portion of uncombined alkali." Guyton combats 

 the opinion of Scheele, who did not obferve any decompofition with the muriate and fulphate with bafe of 

 pot-alh, but only with the falts with bafe of foda. 



The difference of opinion between thofe celebrated chemifts arofe from the circiHnftance that one afcer- 

 tained the decompofition only by the efBorefcence, which is peculiar to falts with bafe of foda (Art. VIII.) 

 while the other obferved it in a licjuid } but in the latter inftance it is much more liniited.— B. 



4 without 



