formation of Ammonia, kc. 28 



these processes, observing with regard to the composition of ni- 

 trogen in these experiments, that till the weight of the substances 

 concerned and produced in these operations are compared, no cor- 

 rect decision on the question can be made : I am anxious to be un- 

 derstood as imitating the caution of one whose judgment stands 

 so high in chemical science ; and, therefore, draw no positive 

 conclusion from the experiment I have described, or from the 

 results I have yet to mention. As, however, I think they may lead 

 to elucidations of the question, I shall venture to give them, not 

 with the minute detail of the preceding experiment, but in a more 

 general manner. 



Potash is not the only substance which produces this effect with 

 the metals and vegetable substances. Soda produces it ; so, also, 

 does lime, and baryta, the latter not being so effective as the 

 former, or producing the phenomena so generally. The common 

 metallic oxides, as those of manganese, copper, tin, lead, ^c., do 

 not act in this manner. 



Water or its elements appear to be necessary to the experiment. 

 Potash or soda in the state of hydrates generally contain the water 

 necessary. Potash dried as much as could be by heat, produced 

 little or no ammonia with zinc ; but re-dissolved in pure water 

 and evaporated, more water being left in it than before, it was 

 found to produce it as usual. Pure caustic lime, with very dry 

 linen, produced scarcely a trace of ammonia, whilst the same 

 portion of linen with hydrate of lime yielded it readily. 



The metals when with the potash appear to act by, or according 

 to, their power of absorbing oxygen. Potassium, iron, zinc, tin, 

 lead, and arsenic evolve much ammonia, whilst spongy platina, 

 silver, gold, ^c, produce no effect of the kind. A small portion 

 of fine clean iron wire dropped into potash melted at the bottom 

 of a tube, caused the evolution of some ammonia, but it soon 

 ceased, and the wire blackened upon its surface ; the introduction 

 of a second portion of clean wire caused a second evolution of 

 ammonia. Clean copper wire, in fused potash, caused a very slight 

 evolution of ammonia, and became tarnished. 



The following, among other vegetable substances supposed to 



