112 THE CANADIAN NATURALIST. [March 



water, and hydrochloric acid added to dissolve the excess of zinc. 

 The amalgam of hydrogen and mercury at once forms in a 

 brilliant voluminous mass, resembling in every way the well-known 

 ammonium amalgam. It is soft and spongy, and rapidly decom- 

 poses, but without any smell of ammonia. The hydrogen escapes, 

 and soon nothing but pure mercury is left in the dish. The 

 experiment appears to show conclusively that an amalgam of 

 hydrogen and mercury can be formed, and that hydrogen is really 

 a metal. It would also throw some doubt upon the existence of 

 the amalgam of ammonium and mercury, and offer an explanation 

 of that compound on the basis of its being the same amalgam of 

 hydrogen and mercury that is prepared in the way now pointed 

 out by Dr. Loew. The smell of escaping ammonia must be traced 

 to some other source than the existence of that radical in combi- 

 nrtion with mercury. — ' Scientific American.^ 



Artificial Production of Ice. By P. H. Vander 

 Weyde, M.D. Calculation of the amount which can he jpio- 

 duced fromi a given ainount of coal in the modern ice machine. 

 — The amount of ice produced by an ice machine, worked by 

 means of an exhaust or condensing air-pump, driven by steam 

 power, is easily determined, theoretically, from the amount of coal 

 burned in the furnace of the steam boiler. It has been proved 

 that the combustion of one pound of anthracite coal produces, in 

 round numbers, 14,000 units of heat, and that in order to freeze 

 water of 72° Fahr., it is necessary to abstract, besides 40*^ of 

 sensible heat, 140® of latent heat — together 180 — which for one 

 pound of water is, of course, equivalent to 180 units of heat. 

 As this number of the units is the eightieth part of the 14,000 

 units produced by the combustion of one pound of coal, it is clear 

 that the heat produced by the combustion of one ton of coal is 

 equivalent to the heat to be abstracted from 80 tons of water of 

 72®, in order to change it into ice. 



But in practice we find here exactly the same state of affairs 

 as is the case with the steam engine. Theoretically, a steam 

 engine ought to produce at least 700 units of force (foot-pounds) 

 for every unit of heat consumed ; in practice, good machinery only 

 produces from about 70 to 100 foot-pounds, from about one-tenth 

 to one-seventh part of the theoretical amount. In the best ice 

 machines thus far constructed, instead of freezing 80 tons of water 

 for every ton of coal consumed^ only from about 8 to 11 tons of 



