53° Experiments and Ohfervations on Shell and Bone. 



Should notice a third 'fubllance, which conftantly occurred in the courfe of my expe- 

 riments. 



When human bones or teeth, as well as thofe of quadrupeds andfifh, whether recent or 

 calcined, were expofed to the a£tion of acids, an efFervefcence, although at times but feeble, 

 was produced. This circumflance at firft I did not particularly notice ; but the following 

 experiments excited my attention : 



After the phofphate of lime had been precipitated from the folutions of various teeth 

 and bones by pure ammoniac, I obferved that a fecond precipitate, much fmaller in quan« 

 tity, was obtained by the addition of carbonate of ammoniac. This fecond precipitate dif- 

 foflved in acids with much effervefcence, during which carbonic acid was difengaged,' and 

 felenite was formed by adding fulphuric acid. Moreover the folution of this precipitate 

 did not contain any phofphoric acid-; nor did the liquor, from which the precipitate had 

 been feparated, afford any trace of it. 



This precipitate was, therefore, carbonate of lime } but I ftill was not certain that it 

 cxifled as fuch in the teeth and bones. » 



Although regular and comparative analyfes of the bones of different animals have not 

 hitherto been made, yet by the experiments of Meflrs, Gahn, Scheele, Macquer, Fourcroy, 

 Berniard, and the Marquis de Bullion, it has been proved that phofphate of lime is the 

 principal offifying fubftance of bones in general, and that this is accompanied by a fmall 

 proportion of faline fubftances, and by fulphatc of lime. 



I was, therefore, defirous to afcertain whether the carbonate of lime, which I had ob- 

 tained by the above mentioned experiments, had been produced from the fulphate of lime, 

 decompofed by the alkaline precipitant, or whether the greater part had not exilled in the 

 bones in the (late of carbonate. 



Each of the folutions in nitric acid aiForded a precipitate with nitrate of barytes ; but the 

 quantity of fulphuric acid thus feparated appeared by far too fmall to be capable of faturat- 

 ing the whole of the carbonate of lime obtained from an equal quantity of the folution. 

 To prove, therefore, the prefence of the carbonic acid, and the confequent formation of 

 carbonate of lime, portions of the various teeth and bones were immerfed at feparate times 

 in muriatic acid ; and the gas produced was received in lime water, by which it was 

 fpeedily abforbed, and a proportionate quantity of carbonate of lime was obtained. 



Although it appears that the principal effeds during offification are produced by tTie 

 phofphate of lime, yet wc here fee that not only fome fulphate, but alfo fome carbonate of 

 lime enters the compofition of bones ; and it is not a little curious to obferve, that as the car- 

 bonate of lime exceeds in quantity the phofphate of lime in cruftaceous marine animals and 

 in the egg-(hells of birds, fo in bones it is vice verfa. It is poffible, when many accurate 

 comparative anaiyfes of bones have been made, that fome may be found compofed only 

 of phofphate of lime ; and that thus fhells containing only carbonate of lime, and bones 

 containing only phofphate of lime, will form the two extremities of the chain. 



I fhall 

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