340 Addilional Experiments' 



per, however, no change of volume was apparent. The hy- 

 drogen evolveiJ, instead of being more than in the former ex- 

 periment, equalled in bulk only '20 grains of mercury. The 

 proiiuction of oxvmuriatic acid was sufficiently evinced by 

 its effect in tarnishing some very small globules of quick- 

 silver, which adhered to the inside of the vessel ; but ibe 

 minuteness of the quantity frustrated an attempt to mea- 

 suie it. From subsequent experiments on similar quan- 

 tities of gas, confined in the same apparatus, it appeared 

 that the eUcirizalion in this last instance had been con- 

 tinued much longer than was necessary ; and that an equal 

 eflfici was produced by ~ the number of electrical dis- 

 charges. 



In this way of making the experiment, the greatest pro- 

 portion of hydrogen gas obtainable fVom niuriatic acid 

 amounted only to about yV^h, u hile, by electrization over 

 quicksilver, -J^ or -j\ was generally evolved. ]t was evident, 

 then, that t^e mercury had considerable influence over the 

 results ; and I found, by experiments with tuiies of dif- 

 ferent diameters, ihai the larger the surfaci^ of the mercury 

 exposed to tlie gas, the more rapid and complete was the 

 change. Its action was greatly accelerated, also, by caus- 

 ing the electric dischar<:e to strike from the conducting 

 wire, sealed into the tube, to the mercury, which uas pro- 

 bably thus raised into vapour ; for, in some instances, the 

 whole of the imier surface of the glass was coated with 

 sublimed calomel. 



The only way in which the mercury appeared to me 

 likely to be efficient in this case, was by rmioving the oxy- 

 muriatic acid as fast as it was formed ; for I have never 

 found any mixture of this gas iti the results of experiiTients 

 on muriatic acid, when carried on over quicksilver. Upon 

 any theory of the constitution of muriatic acid, it may be 

 expected that when, in a mixture of that acid gas with hy- 

 drogen and oxymuriatic acid gases, the two latter come 

 to bear a certain proportion to the former, they will be 

 brought within the sphere of mutuaf agency, and will re- 

 produce muriatic acid. This point appears, from my ex- 

 periments, to be attained, when the hydrogen and oxy- 

 muriatic acid, taken together, have the proportion to the 

 muriatic acid of about 1 to 35. The amount of the chaiiijp, 

 therefore, which is capable of being effected on muriatic 

 acid gas, electrified without the contact of mercury, is li- 

 mited by the reaction of the evolved hydrooen and oxy- 

 muriatic acid eases on each other, whenever they compose 

 a certain proportion of the mixture. This proportion be- 



iner 



