86 Intelligence and Miscellaneous Articles. 



In every case the oxide of iron was completely precipitated, and 

 without a trace of oxide of manganese. The muriates and nitrates 

 of these oxides were similarly treated, and the results were similar, 

 both with the carbonate of lime and with that of magnesia. 



SEPARATION OF PEROXIDE TROM PROTOXIDE OF IRON. 

 BY M. LIEBIG. 



The most distinguished analysts have been occupied with finding 

 a method of separating the oxides of iron. The process proposed by 

 Fuchs is extremely accurate; mixtures of proto- and per-salts of iron 

 are boiled with carbonate of lime ; the peroxide of iron is precipitated 

 in the state of a subsalt, and so com])letely that the solution is not 

 turned red by the sulphocyanate of potash. The only inconvenience 

 of the process is, that the filtered solution, being perfectly neutral, 

 becomes slightly turbid, owing to the conversion of a small portion of 

 protoxide into peroxide. But this may be avoided by using carbonate 

 of magnesia instead of carbonate of lime; the solution does not be- 

 come turbid, and probably because magnesia forms a more stable 

 double salt with the protoxide of iron. 



In some applications this method of separation may be of impor- 

 tance. Calico-printers, as is well known, employ pyroiignite of lime 

 to produce very different tints, and these depend upon the proportion 

 of peroxide which it contains, and this is easily determined by the 

 following process: Take two equal portions of pyroiignite of limej 

 one of them is peroxidized by means of a solution of chlorine, or by 

 ebullition with nitric acid ; then precipitate by ammonia, which gives 

 the entire quantity of iron dissolved ; the other portion is to be boiled 

 with carbonate of magnesia, and then filtered ; the protoxide of iron 

 is afterwards converted into peroxide by the means above mentioned, 

 and precipitated by ammonia, after having added a certain quan- 

 tity of muriate of ammonia to prevent the precipitation of the mag- 

 nesia. The weights of these two precipitates, after subtracting 

 the second from the first, will give with sufficient accuracy the pro- 

 portions of prot- and per-oxide. 



SEPARATION OF PEROXIDE OF IRON FROM THE OXIDES OF 

 COBALT AND NICKEL. BY THE SAME. 



Neither carbonate of magnesia nor that of barytes can be employed 

 for this separation, because the salts of these two bases are entirely 

 decomposed, and the oxides precipitated by them. But carbonate 

 of lime may be advantageously used. 



PREPARATION OF METALLIC CHROME. BY THE SAME. 

 When dry ammoniacal gas is passed over the triple compound of 

 chloride of chrome and ammonia, heated to redness in a glass tube, 

 it is completely decomposed, and black pulverulent metallic chrome 

 is obtained, which acquires a metallic lustre when burnished, burns 

 when heated to redness, and gradually going out becomes a brown 

 powder. 



