126 Scientific Intelligence. 
The mixture contained AsOs 33°15, and CaO, SOs 66°85; the anal- 
ysis gave AsOs 33°14, and CaO,SOs (by difference) 66 86.-—Ann. 
der Chemie und Pharmacie, inkiey’s 265. 
metric determination of manganese.—KricEr has —_— in 
Bunsen’s laboratory the application of the volumetric metho 
termination of manganese more especially when combined with other 
oxyds. The method of determining the quantity of manganese in the 
common deutoxyd will serve as an example of the process employed. 
A few pari pee of the oxyd are introduced into a small flask which 
e 
dissolved in the excess of ‘iodid of aon and colors the solution 
rown. A evolution of chlorine has ceased, a measured portion 
of the normal solution of sulphurous acid is added till the brown color 
has vanished. e excess of sulphurous acid added is then determined 
drops of a clear solution of starch having been added. The quantity 
of this solution required to oxydize one measure of the normal Selgin of 
pe acid having been ea quantity of manganese 
may be calculated. It is well known that the oxyds of manganese are 
all converted by ignition into MnsOs. In the presence of strong bases, 
however, this is not always the case, and a special investigation of this 
point was necessary. Kriiger obtained the following results. To de- 
termine eaten in the presence of iron, the iron is to be peroxydized 
and the two oxyds precipitated together by carbonate of soda: the ai 
Cipitate is to ree ell washed, dried and ignited, and then the manganes 
determined volumetrically. ‘tis present as insOa, The ieee 
the precipitate washed, d ried hed. The manganese in a 
weighed portion of vo uredeante may then be determined volumetri- 
cally : it is present n2Qs. The results obtained by the method in 
question are fedintkabty accurate.—Ann. der Chemie und Pharmacie, 
Ixxxvii, 257. 
