54 Browning — Method for the Quantitative 



It is possible, therefore, that the real cause of insolubility is 

 to be sought in the oxidation of the amyl alcohol and conse- 

 quent formation of an organic acid, and, subsequently, of the 

 corresponding calcium 'salt, but the amounts of the residue 

 were so extremely small that it was not practicable to solve 

 this question, at once, exactly and satisfactorily without direct- 

 ing attention too far from the main issue. Moreover, the 

 error introduced by this peculiar behavior of the calcium salt 

 proved to be insignificant in its effects upon the quantitative 

 determination of the calcium, and accordingly, it was dis- 

 regarded in the subsequent tests. 



The next experiments were directed toward a separation of 

 strontium and calcium nitrates. Definite amounts of a solu- 

 tion of strontium nitrate were measured from burettes into 

 counterpoised beakers and weighed, as already described, the 

 calcium nitrate was then added in solution, and the weight 

 taken again. The water was evaporated and the dry salts dis- 

 solved again in the least possible amount of water, and boiled 

 with amyl alcohol, (30 cm. 3 ) as before. The strontium salt 

 was filtered off into a perforated platinum crucible containing 

 an asbestos felt, dried and weighed as previously described. 

 The calcium was determined in the form of the sulphate, by 

 evaporation of the alcohol, treatment with an excess of sulphu- 

 ric acid, and ignition. 



Correction was made for the solubility of the strontium 

 nitrate, and its consequent presence with the calcium, by cal- 

 culating the amount dissolved in the portion of amyl alcohol 

 employed to the condition of sulphate and subtracting that 

 quantity from the apparent amount of calcium sulphate found. 

 The results of this mode of proceeding are recorded in experi- 

 ments (10) and (11). 



SrO taken. SrO found. Error. CaO taken. CaO found. Error, 



(corrected.) (corrected.) 



(10.) 0-0911 grm. 0-0932 grm. 0"0021 grm. + 0-0932 grm. 0-0907 grm. 0'0025 grm.— 

 (11.) 0-0915 grm. 0-0945 grm. 0-0030 grm. + 0-0933 grm. 0-0899 arm. 0-0034 grm.— 



After making the correction in the manner specified it is 

 evident that the amount of strontium indicated is greater than 

 that originally taken. It is apparent, therefore, that the stron- 

 tium nitrate must have been contaminated, probably mechani- 

 cally, by the calcium salt, as the calcium salt is found to be 

 correspondingly deficient in amount. It was thought best, 

 therefore, to have recourse to a double treatment with the 

 alcohol. Accordingly after the first boiling already described 

 the alcohol carrying the greater part of the calcium in solution 

 was decanted upon an asbestos felt under the conditions pre- 

 viously described and collected in a beaker placed to receive 



