RECENT PROGRESS IN PHYSICS. 413 



understand.) The residue could not be examined, because it acted 

 both upon the platinum and upon the glass 



Hydrogen contracted very much, sometimes to one-tenth of the 

 original volume. The cause of this contraction was a small quantity 

 of oxygen, with which hydrogen gas is nearly always contaminated. 

 Phosphorus brought in to the most carefully prepared hydrogen emits 

 vapors of phcisphorous acid, shines in the dark, and produces a slight 

 contraction. But even after this, the ignited wire produces a further 

 contraction. The phosphorus, therefore, cannot remove all the oxygen 

 from the hydrogen. 



After this experience Grove doubts the correctness of the values 

 ascertained for the atomic weight of hydrogen. 



According to these experiments it seems that it would be more 

 advantageous to use the platinum wire ignited by the galvanic cur- 

 rent, than the electrical spark in eudiometric experiments. 



Hydrogen and carbonic acid mixed in equal volumes were easily 

 affected by the ignited wire. They contracted to 0,48 of the original 

 volume ; the residue was carbonic oxide. One equivalent of oxygen 

 and 1 of hydrogen had, therefore, combined together. 



Carbonic oxide exhibited a remarkable phenomenon. Carefully 

 purified from any carbonic acid, it was exposed to the action of the 

 ignited wire over distilled water, and its volume increased from one- 

 fifth to one-third, according to the intensity of ignition. 



When the gas was dry and confined over mercury, this increase of 

 volume did not take place ; it must have been dependent, therefore, 

 upon the presence of aqueous vapor ; and, in fact, the increase of 

 volume was found to be caused by the formation of carbonic acid. By 

 agitation with caustic potash or lime water the gas was reduced to 

 exactly its former volume ; but then it was found to be mixed with 

 a volume of hydrogen equal to that of the carbonic acid absorbed. 

 This is explained in the ioUowing manner : " Half a volume or one 

 equivalent of oxygen derived from the vapor of the water had com- 

 bined with one volume or equivalent of carbonic oxide, and formed 

 one volume or equivalent of carbonic acid, leaving in place of the car- 

 bonic oxide, with which it had combined, the one volume or equiva- 

 lent of hydrogen with which it had been originally associated." 



On comparing this experiment with the previous one, the singular 

 inversion of affinity under circumstances so nearly similar will appear 

 surprising; in the former case hydrogen abstracted oxygen from car- 

 bonic acid in order to form water, leaving carbonic oxide, while in the 

 latter the carbonic oxide takes the oxygen trom the aqueous vapor to 

 form carbonic acid and leaves hydrogen. 



A more exact idea of the nature of these reactions has not yet been 

 obtained. By the latter experiment, in which a decomposition of 

 aqueous vapor also took place, G-rove was led to the idea that it might 

 be possible to decompose aqueous vapor and produce detonating gas 

 simply by means of the ignited wire. He succeeded in this as will be 

 seen in the following : 



§ 62. Decomposition of aqueous vapor by ignited platinum luire. — 

 Grove discusses the decomposition of aqueous vapor into its elements 

 in the same memoir in which he treats of the action of the ignited 



