382 M. Austin — On the estimation of Manganese. 



Akt. XLYIII. — On the Estimation of Manganese separated as 

 the Carbonate ; by Martha Austin. 



[Contribution from the Kent Chemical Laboratory of Yale University— LXIX.] 



The estimation of manganese precipitated as the manga- 

 nous carbonate, when that salt is obtained by the action of 

 sodium or potassium carbonate, has been regarded as very 

 undesirable for the reasons that, even if the conditions of the 

 precipitate is such that it does not run through the filter, the 

 manganous carbonate can never be freed entirely from alkaline 

 salt, and that the conversion of the carbonate to the manganoso- 

 manganic oxide — the form in which it is customary to weigh — 

 is too uncertain. It had been supposed, also, that the presence of 

 ammoniacal salts (as well as of carbonic acid) causes solution of the 

 manganous carbonate, until the work of Guyard (Hugo Tamm)* 

 showed that when the precipitation is accomplished by ammo- 

 nium carbonate, even in the presence of ammonium chloride, 

 complete separation of the manganese is possible. No data 

 are given by Guyard to show the completeness of the separation 

 of the manganese by this process ; but, Freseniusf examined 

 the method and speaks favorably of it. In this process the 

 main difficulty of the older method of estimation as the carbo- 

 nate — viz., the inclusion of the alkaline salt — is avoided. We 

 know now how to avoid the difficulty in the way of weighing 

 as the oxide by converting that substance to the form of the 

 sulphate, as shown in a former paper.;): 



For a careful study of the separation of manganous carbo- 

 nate by Guyard's method a solution of pure manganous chloride 

 was prepared and standardized as the anhydrous sulphate in 

 the manner detailed in the paper to which reference has been 

 made above. A definite volume of the manganous chloride 

 was carefully drawn into a platinum dish and diluted to a 

 volume of 200 cc . To the solution heated to 100° C. ammonium 

 chloride (about 10 grin.) was added and ammonium carbonate 

 in excess. The solution was kept warm until the precipitate 

 subsided, and then was filtered off on asbestos on a perforated 

 crucible under pressure. The presence of ammonium chloride 

 is necessary to insure such a condition of the precipitate that it 

 will not run through the felt. 



Inasmuch as the precipitate was collected under conditions 

 which readily permit an attempt to weigh as the carbonate, a 

 trial of that method was made incidentally. The event proved 



*Chem. News, xxvi, 37. f Zeit. f. Anal. Chemie, 1872, 290. 



J This Journal, IV, t, 209. 



