554 PHILOSOPHICAL TRANSACTIONS. [ANNO 179Q. 



XVIII. Experiments and Observations on Shell and Bone. By Charles Hatcheit, 



Esq.F.R.S. p. 315. 



When shells were examined, they were immersed in acetous acid, or nitric acid 

 diluted, according to circumstances, with 4, 5, 6, or more parts of distilled water ; 

 and the solution was always made without heat. The carbonate of lime was preci- 

 pitated by carbonate of ammonia, or of potash ; and phosphate of lime, if present, 

 was previously precipitated by pure or caustic ammonia. If any other phosphate, 

 like that of soda, was suspected, it was discovered by solution of acetite of lead. 

 Bones and teeth were also subjected to the action of the acetous, or diluted nitric 

 and muriatic acids. The dissolved portion was examined by the above-mentioned 

 precipitants ; and, in experiments where the quantity of the substance would per- 

 mit, the phosphoric acid was also separated by nitric or sulphuric acid. The 

 phosphoric acid thus obtained, was proved, after concentration, by experiments 

 which, being usually employed for such purposes, are too well known to require 

 description. It is necessary moreover to observe, that as the substances examined 

 were very numerous, and my principal object was to discover the most prominent 

 characters in them, I did not, for the present, attempt in general to ascertain 

 minutely the proportions, so much as the number and quality, of their respective 

 ingredients. 



The greater part, if not all, of marine shells, appear to be of 2 descriptions, in 

 respect to the substance of which they are composed. Those which will be first 

 noticed, have a porcellaneous aspect, with an enamelled surface, and when broken 

 are often in a slight degree of a fibrous texture. The shells of .the other division 

 have generally, if not always, a strong epidermis, under which is the shell, princi- 

 pally or entirely composed of the substance called nacre, or mother of pearl. Of the 

 porcellaneous shells, various species of voluta, cypraea, and others of a similar na- 

 ture, were examined. Of the shells composed of nacre or mother of pearl, I 

 selected the oyster, the river muscle, the haliotis iris, and the turbo olearius. 



Experiments on porcellaneous shells. — Shells of this description, when exposed to 

 a red heat in a crucible, about a quarter of an hour, crackled and lost the colours 

 of their enamelled surface ; they did not emit any apparent smoke, nor any smell 

 like that of burnt horn or cartilage. Their figure remained unchanged, excepting 

 a few flaws ; and they became of an opaque white, tinged partially with pale gray, 

 but retained part of their original gloss. The shells which had not been exposed to 

 fire, whether entire or in powder, dissolved with great effervescence in the various 

 acids; and the solution afterwards remained colourless and transparent. But the 

 shells which had been burned, on being dissolved, deposited a very small quantity 

 of animal coal ; by which the presence of some gluten was denoted, though the 

 proportion was too small to be discovered in the solution of the shells which had not 

 been burned. The various solutions were filtrated, and were examined by pure 

 ammonia and acetite of lead ; but I never obtained any trace of phosphate of lime, 



