Gooch and Austin — Estimation of Manganese, etc. 209 



Akt. XXVIII. — The Estimation of Manganese as the Sulphate 

 and as the Oxide ; by F. A. Gooch and Martha Austin. 



[Contributions from the Kent Chemical Laboratory of Yale University — LXYIL] 



The estimation of manganese by the conversion of salts of 

 that element with volatile acids to the form of the anhydrous 

 sulphate by the action of an excess of sulphuric acid, evapora- 

 tion, and gentle heating was formerly a recognized procedure. 

 On the authority of Rose,* however, this method was set aside 

 on account of the supposed difficulty of removing the excess 

 of acid without disturbing the composition of the normal salt. 

 Thus, Oesten, working under Rose's direction, obtained, upon 

 submitting the crystalline hydrous sulphate MnS0 4 . 5H 2 to 

 heat, results which may be summarized and compared with the 

 results obtained by Rose's sulphide method (the ignition of the 

 residue with sulphur in hydrogen) as follows : 



MnS0 4 .5H 2 

 taken, 

 grm. 



1659 



1-481 



0'725§ 0-201 — 



1-430 0-880J; 0-893 0*013— 0'509 0-512 0'OOS — 



f Ignited gently. % Ignited at low red heat. § Ignited at strong red heat. 



The residues remaining after the gentle ignition of the sul- 

 phate weighed apparently several milligrams more than should 

 have been the case if the salt had been reduced to the normal 

 anhydrous sulphate. At higher temperatures the sulphate 

 turned brown and lost altogether too much w T eight. A com- 

 parison of the errors of the process in which the ignition was 

 at low temperature with those of the sulphide process would 

 seem to justify Rose's rejection of the former method for the 

 latter. Upon recalculating these results, however, using atomic 

 weight in use at present — viz : Mn = 55, S = 32*06, O = 16 — 

 it becomes plain that the errors of the two processes, as shown 

 in Oesten's work, are not very different numerically, though 

 with opposite signs. 



MnSC-4 







MnS 







found. 



Theory. 



Error. 



found. 



Theory. 



Error. 



grm. 



grm 



grm. 



grm. 



grm. 



grm. 



l-043f 



1-037 



0-006 + 



0-597 



0-595 



0-002 + 



1-02 3 J 





0-014 — 









0-934f 



0-926 



0-008+ 









0-905J 





0-021 — 









MnS0 4 .5H 2 MnS0 4 





MnS 







taken. 



found. Theory. 



Error. 



found. 



Theory. 



Error. 



grm. 



grm. grm. 



grm. 



grm. 



grm. 



grm. 



1-659 



1-043 1-039 



0-004 + 



0-597 



0-599 



0-002- 



1-481 



0934 0-928 



0-006 + 









1-430 







0-509 



0-516 



0-007- 



* Ann. d. 



Phys. u. Chem , ex, 125. 











Am. Jou] 



i. Sci. — Fourth Series, 



Yol. Y, No 



27.— March, 1898. 







14 











