OF ZINC AND ANTIMONY. 363 



ably rapid decomposition of water obtained by means of alloys which have been previ- 

 ously acted upon by dilute hydrochloric or sulphuric acids, even after the excess of 

 acid and the salts formed have been completely removed by repeated washings. This 

 decomposition is so rapid, that I have obtained from 200 grammes of an alloy contain- 

 ing 43 per cent of zinc, prepared as just described and boiled with water, nearly a litre 

 of gas in ten minutes. It is plain that the antimony acts here exactly as the platinum 

 in the previous experiments, by forming a galvanic circuit with the alloy. A set of ex- 

 periments was made with alloys, which had been acted upon by acids, similar to those 

 the results of which are given in the table. The irregularities, however, which re- 

 sulted from the unequal action of the acids on the different alloys, from the differences 

 of surface, and from other causes, rendered the final results so discordant, that they 

 were of no value for comparison. They were always much greater than those obtained 

 by using platinum, with the exception of pure zinc, whose decomposing power was not 

 increased by the action of acids. 



This new mode of decomposing water is of value as a process for preparing pure 

 hydrogen, and also for illustrating the composition of water to a class. My mode of 

 preparing the alloy for making pure hydrogen is simply thus. I melt together equal 

 parts of zinc and antimony free from arsenic (this alloy being nearly as active after 

 having been treated with acid as the alloy of 43 per cent of zinc), and granulate as 

 finely as possible. I place the granules m a deep porcelain basin, and pour over them 

 enough hydrochloric acid of ordinary strength to cover them. An energetic action en- 

 sues, which I allow to continue until it becomes weak, and the acid nearly exhausted. 

 The excess of acid, and also the chloride of zinc formed, I now wash away by allowing 

 a stream of water to pour into the basin until it runs off clear and tasteless. The al- 

 loy thus prepared is ready for use. It will evolve hydrogen from boiling water with 

 almost as much rapidity as zinc and dilute sulphuric acid, and even after the tempera- 

 ture of the water has fallen to that of the air, the evolution continues, though only very 

 slowly. A flask containing about 500 grammes of the prepared alloy covered with 

 water continued to evolve hydrogen during the winter for over two months, when the 

 temperature was seldom above 4° C. 



The rapidity of the evolution of hydrogen from the alloy and boiling Avater dimin- 

 ishes quite rapidly, and finally, after several hours, ceases altogether, from the forma- 

 tion of a coating of oxide on the surfaces. The activity can be restored by dissolving 



off this coating with dilute acids. Wliere, however, the alloys contain a large per cent 



« 



of antimony (above 50), the activity cannot be renewed indefinitely in this way, since 

 the particles of antimony set free by the acid adhere to the surface of the alloy, and 



