1*70 COMBUSTION OF CflARCOAL AfcD OF HIDROGEN. 



. *ary for burning the 'inflammable gas and* all the combusti- 

 ble. It is omious, that the proportion of this hidrogen 

 gas cannot be otherwise thW Vfcfy small: but the electric 

 spark will nof^ occasion its entire disappearance. The pre- 

 sence of this gas can be demonstrated 'only by the process 

 given by Messrs. Humboldfahd Gay-Lussac for determin- 

 ing the combustion of a very small proportion of hidrogen 

 in another gas. This process consists in adding 100 parts 

 of hidrogen to 200 of the air' to be analysed, and detonat- 

 ing the mixture with a given quantity of oxigen gas, which 

 must be som'etfhat more than sufficient for burning the hi- 

 drogen. If this detonation .cause a greater diminution than 

 would result from burning the 100 parts of hidrogen added, 

 it is to be concluded, that the gas analysed contained hidro- 

 gen gas. On this subject I shall make a few observations, 

 to which it is of importance to attend. 



The residuum of the detonation sliould be treated with 

 potash, to find whether the combustion of the hidrogen gas 

 that may be discovered furnished any carbonic acid, that 

 no sensible quantity of carbon in the analysis may be ne- 

 glected : but the estimation of the acid gas thus formed 

 cannot be accurate, unless we deduct the carbonic acid, 

 which the hidrogen gas used as a reagent, and deemed pure, 

 always furnishes by its combustion, when this is effected 

 with a surplus of oxigen gas. 

 Experiments J have found to my surprise, that every kind of hidrogen 

 gas obtained in £ as supposed p Ur e furnishes, when completely burned, a 

 various ways, sensible quantity of carbonic acid gas. I have tried hidro- 

 gen gas obtained from the purest iron by means of sul- 

 phuric acid diluted with distilled water; that obtained by 

 a similar process from zinc purified by sublimation ; that 

 from solution of tin by muriatic acid; thai from the de- 

 composition of ammonia in a redhot tube ; and lastly, that 

 from the decomposition of distilled water by Volta's pile, 

 using platina conductors, and arranging the apparatus so 

 that only mercury, platina, and glass were in contact with 

 the water, and with the gasses produced. Each of these 

 kinds of hidrogen gas, when burned with an excess of oxi- 

 gen, always produced a gaseous residuum wljich Was partly 

 absorbed by potash, and rendered Darytes "water turbid by 



forming 



