CARBON AX I M P ~ l ~ I T IkX' HYDltOGEN AFFECTIK'G D E T E R M I N A T I O N O F ATO3lIC WEIC'IIT.
BY
PROP.
E.
w.MOIILEY.
It is very difficult t o obtain hydrogen free from carbon. if zinc is employed. 1. If zinc be dissolved in dilute acids, carbon contaminates t h e escaping hydrogen. No sample of zinc yet obtained by t h e writer gave hydrogen in which carbon was not quickly shown by passing it over heated copper oxide a n d into lime water. 2. If zinc bc amalgamated, p u t i n t o dilute acid and hydrogen obtained electrolytically, i t still contains carbon, which has been proved in t h e same way. 3. If tlie purest zinc obtainable in commerce is heated in a vacuum, it gives off a g a s containing carbon not in t h e form of t h e dioxide. lh. William €1. Burton kindly made many experiments on this matter : sixty granimes of zinc gave sometimes 0.8 C.C. carbon dioxide by combustion of carbon existing in t h e gas given off on fusion i n some form other t h a n carbon dioxide. All Samples also gave otf nitrogen. 4. It is obvious t h a t metallic aluminium is likely t o contain gases imprisoned in it and derived from metallurgical processes. 5. T h e electrolysis of an alkaline hydroxide is likely to give a n impure liydrogen unless alkaline caj:bonates be removed. Such electrolysis, where a carbonate had been purposely added, in a voltameter most thoroughly cleaned from all organic matter, gave hydrogeii containing a iiotable aniount of carbon. T h e bearing of these facts 011 the determination of t h e atomic weiglit of hydrogen is obvious. 276
