384 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



Thus, diluting the ammonia had the beneficial effect which was ex- 

 pected. In the presence of so much oxalate the solution was, of com m . 

 practically free from calcium, hence this result indicates a distinct 

 improvement. 



It has been already noticed that dilution of the original solution has 

 beeu found by others to lessen the amount of magnesium carried down. 

 This fact might have been easily predicted by the hypothesis that the 

 phenomenon is regulated by the Distribution Law. It is further verified 

 by two experiments given below, in which the method of Experiments 

 13-17 was repeated, except that the volume was 800 c.c. instead of 

 200 c.c. 



The Effect of Dilution. 



No. of 

 Experiment 



Weight of 

 Mixed Oxides. 



18 

 19 



0.230'J 

 0.2371 



Weight of CaO 

 taken. 



0.2358 



Weight of 

 MgO. 



0.001 1 

 0.0013 



Error. 



0.42% 

 0.54 ; 



Average error, 0. 1- 



Ilere also no calcium could be recovered from the mother liquor, hence 

 it is clear that the dilution was really of service, reducing the magnesic 

 oxide from 0.74 per cent to 0.4S per cent. The theoretical diminution 

 to less than a quarter of the former value was not to have been expected, 

 for the addition of the ammonia in finite dilution introduces an irregu- 

 larity for which it is impossible to make quantitative correction. 



At this stage in the work it was found that a method of precipitation 



entially identical with that just given had already been published by 

 Professor II. 1'. Talbot in his admirable treatise on the elements of 

 Quantitative Analysis.* So far as we know, no account of it is to be 

 found elsewhere. Since no examples accompany this publication, the 

 preceding work, which was wholly Independent, affords useful confir- 

 mation "I his method as an approximate one for rapid work. 



The chief difference between the method of Talbot and ours lay in the 

 respective amounts of oxalate, a much larger amount having been used 

 in our work in order to insure the total precipitation of the calcium. 



It i- clear from the above account that this large initial 6XCe88 of the 



• Talbot, Quantitative Analysis (Macraillan), 3d ed p 12 (1899). 



