XXXIV. On the ultimate analysis of vegetable and animal substances

• Published in: Philosophical Transactions of the Royal Society of London
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1822
• Subjects: Endeavour; Carbonic acid
• Online Access: http://dx.doi.org/10.1098/rstl.1822.0035; https://royalsocietypublishing.org/doi/pdf/10.1098/rstl.1822.0035

The improvements lately introduced into the analysis of vegetable and animal compounds, with the investigation of the equivalent ratios, in which their constituent elements, carbon, hydrogen, oxygen, and azote are associated, have, thrown an unexpected light into this formerly obscure province of chemical science. While the substitution by M. Gay Lussac, of black oxide of copper for the chlorate of potash, has given peculiar facility and elegance to animal analysis, it may be doubted whether, in those cases, where the main object of inquiry is the proportion of carbon, it has not, fre­quently, led to fallacious results. As the quantity of this element is inferred from the volume of carbonic acid evolved in the decomposition of the organic matters, such of their particles as happen not to be in immediate contact with the cupreous oxide, will remain unconverted into carbonic acid; and thus the proportion of carbon will come to be under­ rated an accident which cannot occur with chlorate of potash, since the carbonaceous matter is here plunged in an ignited atmosphere of oxygen. It is probably to this cause, that we must refer the discrepant results in the analysis of pure sugar, between M. M. Gay Lussac, Thenard, and Berzelius, on the one hand, and Dr. Prout, on the other the former gentlemen assigning about 43 parts in the hundred of car­bon, while the latter states the carbon at only 40. The objects of the present paper are, first to indicate, and endeavour to remove several sources of fallacy attending the method with peroxide of copper; and next, to exhibit the results of its application to a considerable series of vegetable and animal compounds.