144 PRINCIPLES OF CHEMISTRY 



Although gaseous hydrogen does not act directly 43 on many sub- 

 stances, yet in a nascent state reaction often takes place. Thus, for 

 instance, water on which sodium amalgam is acting contains hydrogen 

 in a nascent state. The hydrogen is here evolved from a liquid, and at 

 the first moment of its formation it must be in a condensed form. 44 



Sulphuric acid is poured into the space between the bell and the sides of the outer glass 

 cylinder, and will thus compress the gas in the bell. If the cock of the cylinder be 

 opened the gas will escape by it, and will be replaced by the acid, which, coining into 

 contact with the zinc, evolves hydrogen, and it will escape through the cock. If the 

 cock be closed, then the hydrogen evolved will increase the pressure of the gas in the 

 bell, and thus again force the acid into the space between the bell and the walls of the 

 outer cylinder. Thus the action of the acid on the zinc may be stopped or started at 

 will by opening or shutting the cock, and consequently a stream of hydrogen may be 

 always turned on. Now, if a piece of spongy platinum be placed in this stream, the 

 hydrogen will take light, because the spongy platinum becomes hot in condensing the 

 hydrogen and inflames it. The considerable rise in temperature of the platinum depends, 

 among other things, on the fact that the hydrogen condensed in its pores comes into 

 contact with previously absorbed and condensed atmospheric oxygen, with which hydrogen 

 combines with great facility in this form. In this manner the hydrogen cigar-light gives 

 a stream of burning hydrogen when the cock is open. In order that it should work 

 regularly it is necessary that the spongy platinum should be quite clean, and it is best 

 enveloped in a thin sheet of platinum foil, which protects it from dust. In any case, 

 after some time it will be necessary to clean the platinum, which may be easily done by 

 boiling it in nitric acid, which does not dissolve the platinum, but clears it of all 

 dirt. This imperfection has given rise to several other forms, in which an electric 

 spark is -made to pass before the orifice from which the hydrogen escapes. This is 

 arranged in such a manner that the zinc of a galvanic element is immersed when 

 the cock is turned, or a small coil giving a spark is put into circuit on turning the 

 hydrogen on. 



45 Under conditions the same as those in which hydrogen combines with oxygen it is 

 also capable of combining with chlorine. A mixture of hydrogen and chlorine explodes 

 on the passage of an electric spark through it, or on contact with an incandescent sub 

 stance, and also in the presence of spongy platinum ; but, besides this, the action of light 

 alone is enough to bring about the combination of hydrogen and chlorine. If a mixture 

 of equal volumes of hydrogen and chlorine be exposed to the action of sunlight, com- 

 plete combination rapidly ensues, accompanied by a report. Hydrogen does not combine 

 directly with carbon, neither at the ordinary temperature nor by the action of heat and 

 pressure. But if an electric current be passed through carbon electrodes at a short 

 distance from each other (as in the elecric light or voltaic arc), so as to form an electric 

 arc in which the particles of carbon are carried from one pole to the other, then, in the 

 intense heat to which the carbon is subjected in this case, it is capable of combining 

 with hydrogen. A peculiar-smelling gas, called acetylene, C.,H..>, is thus formed from 

 carbon and hydrogen. 



44 There is another explanation for the facility of the reactions which proceed at the 

 moment of separation. We shall afterwards learn that the molecule of hydrogen contains 

 two atoms, H 2 , but there are elements the molecules of which only contain one atom 

 for instance, mercury. Therefore, every reaction of gaseous hydrogen must be accom- 

 panied by the dissolution of that bond which exists between the atoms forming a mole- 

 cule. At the moment of evolution, however, it is supposed that free atoms exist, and 

 for this reason, according to the hypothesis, act energetically. This hypothesis is not 

 borne out by facts, and the conception of hydrogen being condensed at the moment of 

 its evolution is more natural, and is in accordance with the fact (Note 12) that com- 

 pressed hydrogen displaces palladium and silver (Brunner, Beketoff) that IP, acts as at 

 the moment of its evolution. 



