T. M. Chatard on new Analytical Methods. 419 



§ 4. On the Determination of small quantities of Manganese. 



The delicacy of Crum's test for manganese is well known, 

 but it is believed that no attempt has hitherto been made to 

 employ it as a method of quantitative determination. The fol- 

 lowing work was, therefore, undertaken with that view. 



A standard solution of ammonic oxalate was prepared, of 

 which 1 c. c. =0-0005467 grm. Mn. A sample of dolomite was 

 taken, and four portions were weighed out. These were dis- 

 solved in nitric acid, and a small quantity of plumbic peroxide 

 added to each. On boiling, the bright color of hypermanganic 

 acid appeared. The solutions were passed through small lilters 

 of asbestos with the aid of a Bunsen's pump, and the hyper- 

 manganic acid was determined by means of a standard solution 

 of ammonic oxalate with the following results : 



In a sample of limestone from White Horse, Chester, Co., Pa. 

 e analysis showed 



Mean = 1 99 p. c. Mn. 



But the method, though giving good results where the per- 

 centage of manganese is small, fails when any large amount of 

 that metal is present. Well dried manganous pyrophosphate 

 )vas treated with sulphuric acid, as nitric acid, though dissolv- 

 ing It, was found not to decompose it, little or no hypennan- 

 g^nic acid being formed when the plumbic peroxide was added. 

 With sulphuric acid, the red color of hypermanganic acid was 

 produced, but it was found that not even long boiling sufficed 

 wr total oxydation. 



This was also the case with an alloy of iron and manganese, 

 ^he longer it was boiled, the more hypei-manganic acid was 

 formed, but there seemed to be no definite limit No concord- 

 ant results having been reached, and a well marked end reac- 

 t'^- - such cases being hard to obtain, the method as applied 

 i given up. 



to general analysis waogxv.x.^^,. . t, . i, 



there seems to be, however, reason to maintain that when 

 ^ne quantity of mano-anese is very small, the method will be 

 lonnd both easy and° accurate Perhaps by some modification 

 of the process, it may be made to apply also to the cases in 

 ^nich large quantities of manganese are present. 

 In conclusion, I desire to acknowledge my indebtedness o 

 W. Gibbs for his careful supervision and many valuable 



