104 Chronicles of Science. [Jan., 



Mr. Mallet has continued his experiments on the production of 

 oxygen, and has now modified his process in such a manner that he 

 can also obtain chlorine on a large scale. As certain novel or hut 

 slightly known reactions have brought this process into some note, 

 a few explanations are necessary. The fixation of atmospheric oxygen 

 upon protochloride of coj)per allows two results to ensue ; either the 

 disengagement of oxygen, supposing the desired end be to collect 

 that gas, or the decomposition of chlorhydric acid and liberation of 

 chlorine, should the production of that body be desired. The 

 absorption of oxygen by protochloride of copper is spontaneous, and 

 takes place at the ordinary temperature in a few hours, provided 

 the air be sufficiently moist, and especially if the sui'faces be renewed. 

 If the temperature be raised the absorption is more rapid, and this 

 is the most important part of the question, for by raising the tem- 

 peratiu'e to between 100^ and 200° C,, or even higher, in the presence' 

 of steam, absorption may be regarded as ahuost instantaneous. 



If upon protochloride of copper, heated to 100" or 200°, com- 

 mercial chlorhydric acid be slowly dropped, steam alone will be 

 disengaged, and supposing the addition of acid to be slow enough, 

 and the access of air and renewal of surface sufiicient, the odour of 

 chlorhydric acid will be scarcely perceptible, and the whole proto- 

 chloride will transform into anhydrous bichloride, which, when 

 heated in a close vessel, instantly disengages chlorine. The simul- 

 taneous absorption of oxygen and chlorhydric acid is an imjiortant 

 and interesting fact, because the extraction of the chlorine from the 

 acid takes place in this case by means of the atmospheric air, and in 

 an absolutely direct manner. With gaseous chlorhydi'ic acid the 

 action is the same, in fact better, provided the acid gas contain, as is 

 always the case, a certain quantity of steam, and that the accession 

 of air be sufficient. The presence of water is necessary to the 

 absorption of oxygen by protochloride of copper. Oxidation and 

 chlorination take place very quickly at high temperatures, but the 

 great advantage is that they yield dry products, which is very con- 

 venient, inasmuch as steam is frequently a source of inconvenience 

 and alteration of apparatus. From a manufacturing point of view, 

 it may be considered that 100 kilogrammes of protochloride of 

 copper, mingled with sufficient inert matter to facilitate manipula- 

 tion, will produce practically fi'om three to three-and-a-half cubic 

 metres of oxygen, or fr'om six to seven cubic metres of chlorine. 

 As four or five operations at least may be performed in twenty-four 

 hours, it is plain that 100 kilogrammes of substance will produce 

 from fifteen to eighteen cubic metres of oxygen, or from 200 to 300 

 kilogrammes of chloride of hme, in tweuty-fom- hours. 



The price of the raw material does not exceed one franc the 

 kilogiamme, and the loss is ascertained by experience to be always 



