Expifimntts »H carbonated Hydrogen Gas, 243 



maWe, and in another that it fupported combuftion like vital air. I need hardly remark, 

 that a fatisfaftory analyfis cannot be attained of any fubftance, without the moft fcrupulous 

 regard not only to the qualities, but to the precife quantities of the produdls of our opera- 

 tions. 



To the 8th and 9th experiments the objeftion may be urged with additional weight, 

 which has been brought againft the preceding ones, that the quantity of oxygen, inftead of 

 being duly increafed in the combuftion of the eledtrified gas, was on the contrary diminifli* 

 ed. Thus, in the 8th experiment 2,83 meafures of carbonated hydrogen were inflamed with 

 4,58 meafures of oxygenous gas ; but in the pth, though the 2,83 meafures were dilated to 

 |,i6, and had therefore received a confiderable addition of combuftibie matter, the oxygen 

 employed was only 4,09. To the reft of Dr. Auftin's experiments, cither one or both of the 

 above objections are applicable. 



The firft and moft important ftep, therefore, in the repetition of thefe experiments, is to de- 

 termine whether the carbonated hydrogenous gas really fuftains by the procefs of ele£lrization' 

 a diminution of its quantity of carbon; becaufe, fhould this be decided in the negative, we 

 derive from the fa*Sl- a very ufeful direftion in afcertaining the true fource of the evolved 

 hydrogen. The following experiments were therefore made with a view to decide this 

 queftion, and the error of Dr. Auftin in employing too little oxygen was carefull/ 

 avoided *, 



Experiment 1. In a bent tube ftanding inverted over mercury, 94,5 meafures of carbo- 

 nated hydrogenous gas from acetite of pot-afti were tnixed with 107,5 of oxygen. The 

 total, 202, was reduced by an explofion to 128,5, ^"'' ^^'^^ further contradled by lime water 

 1054. A folution of hepar fulphuris left only 23 meafures. 



The diminution by lime water, viz. 74,5 meafures, makes known to us the quantity of 

 carbonic acid afforded by the combuftion of 94,5 meafures of carbonated hydrogenous gas. 

 And the refidue after the a£lion of hepar fulphuris, viz. 23 meafures, gives the proportion of 

 azotic gas contained in the carbonated hydrogen ; for the oxygenous gas employed, which 

 was procured from oxygenated muriate of pot-afli, was fo pure, that the fmall quantity ufed 

 in this experiment could not contain a meafurable portion of azotic gas. 



Experiment 2. The fame quantity of carbonated hydrogen was expanded by repeated 

 eleilrical fliocks to 188 meafures. The addition of hydrogenous gas therefore amounted to 

 93,5. The gas thus dilated was fired at different times with 392,5 meafures of oxygenous 

 gas ; and the refidue after thefe feveral explofions was 203 meafures. Lime water reduced 

 it to 128,5, ^"^ fulphure of pot-afli to 19,5. In this inftance, as in the former one, the 

 produdl of carbonic acid is 74,5 meafures. 



'' The apparatus employed in thefe experiments was the ingenious contrivance of Mr. Cavendifli, and is 

 defcribed in the Ixxvth vol. of the Philofophical Tranfaftions. In dilating; the gas, I fometimes ufcd a 

 ftraight tube, furnilhed with a cenduflor in the manner of Dr. Prieftley (fee his Experiments on At, vol. i. 

 plate I. fig. 16.) The bulk of the gafes introduced, and their volume after the various e.xperiments, were 

 afccrtained by a moveable fcale, and by afterwards weighing the mercury which filled the tube to the marks 

 on the fcale; by which means I was fparcd the trouble of graduating the fyphons. Each grain of mercury 

 Indicates one meafure of gas ; and though the fmallnefs of the quantities fubmitted to experiment may be ob- 

 jefted to, yet this advantage was gained, that the elcftrified gas could be fired at one explofion, as was done iii 

 t!ie 4th, 6th and Sth experiments. Errors from variations of temperature and atmofpherical prelTure were 

 carefully avoided. 



I i 2 Finding 



