Calcium by the Acetate and Bromine Methods. 139 



constituents. That the conditions of the previous analyses 

 might be approximately kept, 5 grams of ammonium chloride 

 and 10 grams of ammonium acetate were added in each case. 

 Only the calcium of the first manganese filtrate was deter- 

 mined. 



w 



3ight of MnO 



Weight of Ca( 



) Weight of CaO 







taken. 



taken. 



found in 1st filtrate. 



Loss. 





grm. 



grm. 



grm. 



grm. 



(19.) 



0-2042 



0-1702 



0-1639 



0-0063 



(•20.) 



0-1020 



0-1705 



0-1638 



0-0077 



(21.) 



0-0508 



0-1702 



0-1662 



0-0042 



(22.) 



0-0207 



0-1702 



0-1682 



0-0018 



(23.) 



0-2039 



0-0848 



0-0779 



0-0069 



(24.) 



0-1020 



0-0849 



0-0831 



0-0018 



(25.) 



0-0516 



0-0855 



lost 





(26.) 



0-0204 



0-0846 



0-0833 



0-0013 



(27.) 



0-2037 



0-0423 



0-0399 



0-0024 



(28.) 



0-1023 



0-0427 



0-0421 



0-0006 



(29.) 



0-0512 



0-0424 



0-0415 



0-0009 



(30.) 



0-0203 



0-0428 



0-0421 



0-0007 



(31.) 



0-2037 



0-0171 



0-0141 



0-0030 



(32.) 



0-1023 



0-0173 



0-0158 



0-0015 



(38.) 



0-0509 



0-0170 



0-0167 



0-0003 



(34.) 



0-0207 



0-0171 



0-0162 



0-0009 



These results indicate that the amount of calcium, carried 

 down with the manganese, depends largely on the relative 

 quantities of manganese and calcium. However this may be 

 it is evident that where the amounts of each are not less than 

 0-02 grams a double precipitation of manganese should be 

 made. 



Having introduced such large quantities of ammonium salts 

 into the solutions the question of effect on the oxalate precipi- 

 tate was raised. Attention has been called to the negative 

 calcium error. Is this due simply to the solubility of the 

 oxalate or is it the sum of large positive* and larger negative 

 errors ? 



In answer to this suggestion a number of calcium determi- 

 nations were made, in which the previous conditions, as to 

 quantity of ammonium salts and volume of solution, were 

 observed. 



* The source of positive error would be the reagents and glass ware. The 

 operations, excepting the precipitation of manganese by bromine, were carried on 

 in platinum. The ammonium hydrate and sulphurous acid were freshly prepared. 

 The other reagents were carefully tested. 



