M. Austin — On the estimation of Manganese. 383 



as Rose* has stated previously, that when the carbonate is 

 gently heated, evolution of carbon dioxide and oxidation of the 

 residue begins before the water is thoroughly removed ; for, 

 though nearly all the results are above the theory, the solution 

 of the residue in hydrochloric acid indicated plainly the pres- 

 ence of a small amount of a higher oxide of manganese. In 

 the following table are found the results of a series of experi- 

 ments in which the attempt was made to weigh "first as carbo- 

 nate and again after strong ignition — well within the oxidizing 

 ilame of a powerful burnerf — as the manganoso-manganic 

 oxide. The application of the bromine test to the hot ammo- 

 niacal filtrate showed, that in every one of these experiments, 

 the precipitation of the manganese in the form of the carbonate 

 had been complete. 



MnC0 3 



Md 3 4 



cm 3 . 



•UU.L±4Vyl 



prm. 



Pound. Theory. 



Error. 



Found. Theory. 



Error. 



50 



10 



0-2685 0-2680 



0-0005 -f- 



0-1770 0-1776 



0-0006 — 



50 



10 



0-2704 



0-0024 + 



0-1788 



0-0012 + 



50 



10 



0-2710 



0-0030 + 



0-1770 



0-0006- 



50 



10 



0-2720 



0-0040 + 



0-1774 



0-0002 — 



As shown in this table, weighing as the carbonate is out of 

 the question ; the errors of the process when the residue is 

 ignited in the manner described to form the manganoso-man- 

 ganic oxide are much smaller though rather variable. The 

 estimation of manganese as the anhydrous sulphate had given 

 in the work to which reference has been made results agreeing 

 so much more closely than could be obtained by any other 

 method of procedure, that the attempt was made to estimate 

 the amount of manganese precipitated as the manganese carbo- 

 nate by converting it first to the oxide, then to the sulphate. 

 A given weight of sulphate was precipitated as the manganous 

 carbonate, after the employment of all the precautions men- 

 tioned previously in this paper, and then filtered off on ashless 

 filter paper. After washing thoroughly with hot water, the 

 filter was burned, the residue ignited for the condition of the 

 manganoso-manganic oxide and weighed as such. Then the 

 oxide was converted to the sulphate by heating with three or 

 four drops of concentrated sulphuric acid. The agreement of 

 the results as shown in the following table is considerably 

 better. 



* Annal d. Phys. u. Chem., 1851, lxixiv, 52. 

 fThia Journaf, IV, v, 209. 



