154? Intelligence and Miscellaneous Articles. 



Some questions of theory suggested by the above experiments 

 and relating to the rationale of the action of what are termed ' the 

 imponderables' and to terrestrial magnetism, are then briefly dis- 

 cussed, and the author concludes by stating that he considers his 

 experiments prove satisfactorily, that whenever a bar of iron or 

 other magnetic metal is magnetized, its temperature is raised. 



XXI. Litelligence and Miscellaneous Articles. 



ON THE PREPARATION OF PURE OXIDE OF COBALT. 

 BY M. LOU YET. 



n| '^HE author observes that chemists are generally aware that no- 

 J- thing is less easy than to separate oxide of cobalt from the iron 

 and nickel which it contains ; on this account the oxide of cobalt is 

 rarely met with in commerce perfectly free from all traces of these 

 metals. 



Among the methods which have been proposed to obtain from 

 cobalt ores the oxide perfectly free from iron and nickel, M.Liebig's 

 appears to have been preferred. This process, which depends chiefly 

 on the property of suljjhate of cobalt to resist a red heat, whilst the 

 sulphates of iron and nickel are totally decomposed, may undoubt- 

 edly give good results, as applied to ores ; but the author states that 

 his researches in all other cases have failed to produce perfectly pure 

 oxide of cobalt. 



The author found that although sulphate of iron, when exposed 

 alone to a red heat, is perfectly decomposed, yet when mixed with 

 a large quantity of sulphate of cobalt, it sustained it without being 

 decomposed, and consequently without being rendered insoluble ; 

 the heat was very great, and kept up for several hours. If a mixture 

 containing cobalt, but no arsenic, be treated according to M. Liebig's 

 process, the iron, not being converted into an insoluble arseniate, 

 remains in the mass partly in the state of sulphate. This takes place 

 with zafi^re, an arsenical ore of cobalt which has been roasted, and 

 from which the arsenic has consequently been expelled. It results 

 from what is above stated, that the sulphate of iron formed, partially 

 resists the action of the heat, and consequently that the cobalt even- 

 tually obtained contains iron, though completely free from nickel. 



Although processes are already known by which cobalt and iron 

 are separated without much difficulty, the author states that one 

 which he has discovered is so simple, and its employment so certain, 

 that he thinks in making it known he may render service to the arts 

 which include the use of pure oxide of cobalt. 



This 'process depends on the diff'erence which exists between the 

 affinities of oxide of cobalt on one hand, and on the other of the 

 protoxide and sesquioxide of iron for acids ; a diff'erence which is 

 highly advantageous to the first of these compounds. Take a solu- 

 tion of sulphate of cobalt, containing a certain quantity of sulphate 

 of iron, and add to this gelatinous hydi'ate of cobalt at least equiva- 

 lent to the oxide of iron contained in the sulphate ; heat the mixture 



