HYDROGEN AS A GAS AND AS A METAL. 297 



Dr. Andrews, of Belfast, to enormous pressures, and to extremely low 

 temperatures, but without exhibiting- the slightest tendency to conden- 

 sation. Hence it has generally been considered a permanent gas ; but 

 recent investigations, conducted by the master of the British Mint, the 

 learned and distinguished Protessor Graham, tend strongly to show 

 that hydrogen gas, as we meet with it under ordinary circumstances, is 

 really the vapor of a highlj/ volatile metal. 



It may be now generally stated that when a solution containing a 

 metal and a non-metallic body is decomposed by a galvanic current, the 

 metal is usually deposited on the negative pole, and the non- metallic 

 body on the positive electrode. If, for instance, we take a solution of 

 common blue vitriol, or sulphate of copper, and plunge the poles of a 

 battery into the liquid, we find that immediately metallic copper is depos- 

 ited on the wire forming the iie(jative pole, while the sulphuric acid (a 

 non-metallic body) appears at the positive end. If now we plunge the 

 two poles into plain water, which, as we have already seen, is a com- 

 l)ound of hydrogen and oxygen only, the hydrogen appears at the negative 

 pole and the oxygen at the opposite one. We learn, then, in applying 

 the galvanic test, that hydrogen arrays itself on the side of metals, and 

 this fact is completely in accord with the view of its nature referred to 

 above. 



Again, it is a well-known fact that metals are capable of uniting with 

 each other so as to form compounds called alloys ; thus, brass is an alloy 

 resulting from the fusion of the two metals copper and zinc in suit- 

 able proportions. But it is not always necessary that the two metals 

 should be heated together in order to make them combine ; for, if we 

 take a slip of gold and plunge it into some of the liquid metal, 

 mercury, or quicksilver, as it is called, the gold and mercury combine 

 with each other to form an alloy or " amalgam," possessing a strong 

 metallic luster. To go just one step further : if we convert this metal, 

 mercury, into a colorless, invisible gas, which we can do by applying 

 sufficient heat, and if into a vessel filled with this mercury gas we 

 plunge a slip of gold, we find that the two metals combine or amalga- 

 mate nearly as easily as under ordinary circumstances. If, then, "we 

 can accomplish so much with the mercury gas, whose metallic nature is 

 certain, why may we not make hydrogen gas alloy with some metal also ? 



By the very beautiful and interesting discovery that certain metals 

 possess the power of absorbing enormous quantities of hydrogen with- 

 out loss of metallic appearance, Professor Graham has greatly strength- 

 ened the evidence in favor of the metallic nature of hydrogen, and has 

 even gone so far as to calculate the density of the metal, which he calls 

 "hydrogeniura." 



Professor Graham found that certain metals — palladium and platinum 

 more i:)articularly — possess the extraordinary power of absorbing large 

 volumes of hydrogen gas, and retaining it in some kind of combination. 

 In order to demonstrate this, it is only necessary to take a plate of pal- 



