94 On some new Electrochemical Researches 



combination, and one of hydrogen is given off; and in 

 the action of water on potassium to form potash, the same 

 quantity of hydrogen ought to be expelled. From my 

 analysis* of sulphuretted hydrogen, it would appear, that 

 if potassium in forming a combination with this substance 

 sets free hydrogen, it will be nearly the same quantity as it 

 would cause to be evolved from water. And if the analysis 

 of Mr. Proust and Mr. Hatchett, of the sulphuret of iron, 

 be made a basis of calculation, iron, in attracting sulphur 

 from sulphuretted hydrogen, will liberate the same propor- 

 tion of hydrogen as during its solution in diluted sulphuric 

 acid ; and taking Mr. Dalton's Jaw of proportion, the case 

 will be similar with respect to other metals : and if such 

 reasoning were to be adopted, as that metals are proved to" 

 be compounds of hydrogen, because, in acting upon dif- 

 ferent combinations containing hydrogen, they produce 

 the evolution of equal proportions of this gas, then it might 

 be proved that almost any kind of matter is contained in 

 any other. The same quantity of potash, in acting upon 

 either muriate, sulphate, or nitrate of magnesia, will pre- 

 cipitate equal quantities of magnesia; but it would be ab- 

 surd to infer from this, that potash contained magnesia, as 

 one of its elements ; the power of repelling one kind of 

 matter, and of attracting another kind, must be equally de- 

 finite, and governed by the same circumstances. 



Potassium, sodium, iron, mercury, and all metals that I 



* The composition may be deduced from the experiments in the last 

 Bakerian lecture, which show that it contains a volume of hydrogen equal 

 to its own. If its specific gravity be taken as 35 grains, for 100 cubical 

 inches, then it will consist of 227 of hydrogen, and 32*73 of sulphur. When 

 sulphuretted hydrogen is decomposed by common electricity, in very refined 

 experiments, there is a slight diminution of volume, and the precipitated 

 sulphur has a whitish tint, and probably contains a minute quantity of hy- 

 drogen. When it is decomposed by Voltaic sparks, the sulphur is precipi- 

 tated in its common form, and there is no change of volume ; in the last case 

 the sulphur is probably ignited at the moment of its production. In some 

 experiments lately made in the laboratory of the Royal Institution, on ar- 

 seniuretted and phosphuretted hydrogen, it was found that when these gases 

 were decomposed by electricity, there was no change in their volumes ; but 

 neither the arsenic nor the phosphorus seemed to be thrown down in their 

 common state * the phosphorus was dark-coloured, and the arsenic appeared 

 as a brown powder, both were probably hydrurets : this is confirmed like- 

 wise by the action of potassium upon aseniuretted and phosphuretted hy- 

 drogen ; when the metal is in smaller quantity than is sufficient to decom- r 

 pose the whole of the gases, there is always an expansion of volume ; so that 

 arse.iiuretted and phosphuretted hydrogen contain in equal volumes, more 

 hydrogen than sulphuretted hydrogen, probably half as much more, or 

 twice as much more. From some experiments made on the weights of phos- 

 phuretted and arseniuretted hydrogen, it would appear that 100 cubic inches 

 of the first weigh about JO grains, at the mean temperature and pressure, 

 *nd 100 of the second about 15 grains. 



have 



