On the various Combiitatlons of Carbon nv'tth Oxigen. 5 



other inftance I fubflituted lime for the carbonate of lime ; here too the gafeous oxide was 

 obtained, but in much lefs quantity, and had the lime been perfectly pure, it is probable 

 that very little, or none, would have been procured ; this experiment likewife points out 

 the origin of the gas. In invelligating the properties of this inflammable gas, I found that 

 when perfedly free from carbonic acid, it was lighter than common air, in the proportion 

 of 22 to 23. 



That when mixed with common air and ignited, it did not explode, but burnt flowly 

 with a lambent blue flame : that when the produ£ls of this combuftion were collefted, by 

 burning a confiderable quantity in a large receiver containing common air or oxygen gas, 

 nothing but carbonic acid could be colleded, nor was there any perceptible quantity of 

 water condenfed againft the fides of the veflel. That when 20 parts of this gas were mixed 

 with eight parts of oxygen, and ^fired over mercury by the cle£lric fpark, the whole was 

 reduced to 18 or 19 parts, which were found to be carbonic acid gas, being totally ab- 

 forbed by lime water. Hence we fee, that this gas contains rather more oxygen than that 

 produced from charcoal and finery cinder, as 20 parts of it, with eight of oxygen, produce 

 no lefs than 18 or 19 parts of carbonic acid gas ; upon the whole, however, they appear 

 to be very fimilar, more particularly in their fpecific gravities ; but I remarked, neverthe- 

 lefs, that when a confiderable quantity of the gafeous oxide from charcoal, and the different 

 calces was burned in a large receiver, fome moiftwe was depofited on Its fides; there 

 can be little doubt, therefore, that this difference in the refults depends on a portion of 

 hydrogen, which enters more or lefs into the compofition of all common charcoal. 



The flatement at page 7, taken from the foregoing and other experiments, will (hew 

 more correctly the difference between thefe gafes, and fome of the belt known hydrocar- 

 bonates ; from thefe calculations it will likewife appear, that the weight of the gafeous 

 oxide obtained from the decompofition of the carbonic acid, added to that of the pure air 

 recelTary for its faturation, is very nearly equal to that of the carbonic acid gas produced j 

 for 100 cubic inches of this gas weighs 30 grains, and 40 cubic inches of oxygen gas 13.6 

 grains, making together 43.6 grains. Now 92 cubic inches of carbonic acid gas weighs 

 43.2 grains ; a greater degree of correflnefs cannot well be expcfted from experiments of 

 this nature. But by making a fimilar calculation with the produdls obtained from the ex- 

 plofion of the gafeous oxides from charcoal and the metallic calces, it will be found, that 

 the weight of the gafeous oxide,- added to that of the pure air, is greater than the weight 

 of the carbonic acid produced 5 a circumflance which would feem to prove the formation 

 of water, more efpecially when compared with the other experiments already related. 

 From thefe fads, therefore, we would infer, that the pureft gafeous oxide is to be obtained 

 from the decompofition of carbonic acid ; for in this cafe it appears to contain neither 

 yrater, nor the bafis of water. 



Dr. Prieftley, in his obfervations on thefe gafes remarks, that in their properties they 

 are very fimilar to the inflammable air obtained by heat from moiftened charcoal ;- this, 

 however, upon a more particular inveftlgation, I did not find to be the cafe. A quantity 



of 



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