24H i.MCC'iKO-MO'iivi': si:uii:s oi' tiiI': metals. 



into llic ionic form, i.e., as copper sulpliate, by 'being oxidised lo 

 CuO. This, of course, then reacts with the acids to form CiiSO^. 

 Owing to tlie fact that silver is below copper, silver will b& 

 attracted by hot sulphuric acid even less readily tlian capper, and 

 gold and platinum have so little tendency towards oxidation that 

 even hot concentrated li2S04or HNOahas no action. 



Another advantage of this point of view is that it gives us 

 a perfectly i)lausil)le conception of what is generally termed 

 " mascent hydrogen," a term vvbich students accept, but do not 

 as a rule attem])t to understand. 



Sometimes the text-book suggests that the activity of na'-cent 

 hydrogen is due to the fact that the gas is in the atomic state. 

 This, of course, is mere hyp(jthesis, and it is ])ractically impossiljle 

 to test its truth, luirther, it is also bypothesis to assume that 

 atomic hydrogen is more active Ih.an molecular hydrogen, and 

 lastly, this "explanation" leads to ibc deduction that nascent 

 hydrogen from, difTerent metals mn-t he th'; same and possess 

 exactly the same powers. Such is. however, by no means the 

 case. We know that nascent hydrogen from so'.ue metals will 

 i|)erform reductions which the nascent gas from other metals will 

 not, and it is a general empirical rule tliat the biglier the metal in 

 the IClectro-motive Series the greater the rtducing ixower of the 

 nascent hydrogen devek)pe(l at its surface. 



Let us consider a moment what is the driving force which 

 causes the liberation of hydrogen. It is the (hlTerence in position 

 of the metal and hydrogen in the Electro-motive Series. We can 

 regard the hydrogen as being ejected from the acid under a very 

 considerable pressure, a pressure which is all the greater the 

 bigher the position of the metal in the series. According to this 

 view " nascent " hydrogen is practically hydrogen under very 

 great pressure, and it is interesting in this connection to call at- 

 tention to the fact that ordinary hydrogen under great pressure 

 can (]e])Oisit silver from solution, which hydrogen at atmospheric 

 pressure does not do. A simple analogy makes the matter per- 

 haps clearer, at any rate, to the junior student's mind. If we 

 imagine a crowd of people trying to get out of a room with a 

 very narrow door, then, owing to the jiressure of the people be- 

 hind, those in front are projected through the opening with a 

 velocity depending on the magnitude of this pressure. This 

 pressure behind is dependent on the tendency of the persons to 

 get outside, and corresponds to the ionisation tendency of the 

 imetal. The ejected people, again, correspond with the nascent 

 hydrogen. Owing to their energy of ejection they have different 

 properties to people at rest, i.e., possess more energy. 



Tb'us nascent hydrogen developed at the surface of metials 

 high up in the Klectro-motive Series possesses more energy than 

 that from metals lower in tlie series, a.nd this energy is available 

 for the reduction r)f any reducible ])ody ])rescnt. 



We can ap])ly this principle to the action of nitric acid on 

 metjiuls. When a metal is placed in dilute nitric acid. then, if the 

 metal can displace hydrogen, it ])roceeds to ilo so. and develops 



