^ On the various Comhlnatlom of Carbon ivith Oxigen^ 



which diftinguiflies this gas from other inflammable gafes, is the- great proportion of car- 

 bonic acid which it yields when united with oxygen. In the above experiment we find fix 

 meafures of carbonic acid gas generated ; now this quantity would require at leaft feven 

 meafures of pure oxygen, whereas the quantity employed was only 3! meafures ; we muft 

 therefore infer, that the remaining 3! meafures muft have been originally combined with 

 the inflammable gas, conftituting what may be called a gafeous oxide. Hence it would 

 appear, that this gas bears the fame relation to carbonic acid, that nitrous gas does to the 

 nitrous acid. In future, for the fake of diftin£lion, we fliall call it the gafeous oxide of 

 carbone. The gafes obtained from the other metallic oxides and charcoal, were perfectly 

 fimilar in their properties; all of them when mixed with common air and ignited, burned 

 with a lambent blue flame, without any fenfible explofion, and. much carbonic acid, with 

 a little water, was produced. When mixed with nitrous gas no diminution or fenfible 

 charge could be perceived, which proves that their oxygen is in a combined, and not in a 

 difengaged ftate. 



Dr. Prieftley has likewife found, that when the carbonate of barytes was mixed with the 

 grey oxide of iron, and expofed to a ftrong heat in a retort, that not only carbonic acid, but 

 alfo inflammable gas was obtained. In order to fatisfy myfelf with regard to this faft, I 

 mixed a quantity of the carbonate of barytes and oxide of iron, both having been feparately 

 made red hot for feme time, and introduced them into a dry coated glafs retort. Heat 

 being gradually applied, a quantity of gas, which at firfl: was nothing more than carbonic 

 acid mixed with a little azote, efcaped; but when the retort had been red for a few 

 minutes, the gas difengaged confifted of carbonic acid 25 parts, and gafeous oxide of car- 

 bone ten parts ; the whole amounting to 30 ounce meafures. This experiment was re- 

 peated, and an iron retort employed, in order that a much greater degree of heat might 

 be given ; in this cafe, not lefs than 90 ounce meafures of a fimilar mixture of gafes were 

 obtained. 



Conceiving that in thefe experiments the gafeous oxide muft proceed from the partial 

 decompofitions of the carbonic acid by the iron, when raifed to a high temperature, I 

 thought I fliould fucceed better by employing iron filings in place of the grey oxide, as 

 thefe would have a greater affinity for oxigen. Accordingly I took a quantity of common 

 chalk, and expofed it to a low red heat for 10 minutes ; it was them mixed with an equal 

 quantity of clean iron filings made as dry as poffible ; the mixture being-introduced into 

 an iron retort, heat was gradually applied. As foon as the retort became red, gas began 

 to. be difengaged in great abundance, and continued to come over for a conCderable length 

 of time, fo that the whole muft have amounted to many gallons. Portions of this being 

 examined at different periods, it was found to confift on a medium of one part of carbonig 

 acid gas, and four or five parts of gafeous oxide of carbone. 



From this experiment we perceive, that a much greater proportion of gafeous oxide is 

 obtained, and more carbonic acid decompofed, where iron filings are employed in place of 

 the grey calx, which proves that it is the acid which is decompofed by the iron. In an- 

 other 



