124 



was given as thorough a trial as time and opportunity permitted, and although the 

 results obtained were not very satisfactory, the method itself certainly looks very prom- 

 ising. The difficulties are, first, the very small amount of sample taken; second, the 

 extreme proneness of the precipitate to go through the filter; third, the great difficulty 

 of removing the precipitate from the sides of the beaker or casserole; fourth, the diffi- 

 cult v in washing all the nitric acid out of the precipitate. Asbestos is much inferior 

 to paper pulp for filtering. 



W. D. Richardson, Chicago, III.: With the volumetric method, following your 

 directions, we did not have very good success. 



0. M. Shedd, Lexington, Ky.: From my work, I would suggest on samples similar 

 to No. 1 that ammonium hydroxid and ammonium oxalate be added as in the case 

 of mixed fertilizers, and that an aliquot be used of 0.10 to 0.20 gram and not over 

 0.25 gram, instead of 0.50 gram, for the smaller potassium platinic chlorid precipitate 

 can be worked better; besides it is my experience that very large precipitates carry 

 down a greater proportion of impurities. 



In addition to the above results Mr. Shedd made determinations in sample No. 1 

 by evaporating with sulphuric acid, igniting, and then evaporating with platinic 

 chlorid. The results secured were 49.75 and 49.88 per cent. 



M. G. Donk, Washington, D. C.: Could get no satisfactory results on sample No. 1 

 by the volumetric method. 



E. L. Baker, associate referee, made additional comparative determinations of 

 potash in several samples of potash salts, both with and without the use of ammonia 

 and ammonium oxalate, in making up the solution, the results being as follows: 



Comparison of results obtained with and without the use of ammonia and ammonium 



oxalate. 



Mr. Baker also reported results of determinations of potash in a number of samples 

 by the sodium cobalti-nitrite method first proposed as a quantitative process by 

 Adie and Wood." This method involved the use of sodium cobalti-nitrite as a pre- 

 cipitant, and in the original process precipitation was effected in the presence of acetic 

 acid in a solution which should contain from 0.5 to 1 per cent of potash. Drushel *> 

 has modified this method as follows: 



The solution of a potassium salt, containing not more than 0.2 gram of potassium 

 oxid and free from ammonium salt, was treated with a rather large excess of sodium 

 cobalti-nitrite solution, acidified with acetic acid, and evaporated to a pasty condi- 

 tion over the steam bath. It was then cooled and treated with from 50 to 100 cc of 

 cold water, and stirred until the excess of sodium cobalti-nitrite was dissolved. It 

 was allowed to settle and was decanted through a perforated crucible fitted with an 

 asbestos felt. The precipitate was washed two or three times by decantation, after 

 which it was transferred to the crucible and thoroughly washed with cold water. In 

 the meantime a measured excess of standard potassium permanganate was diluted 

 to ten times its volume and heated nearly to boiling. Into this the precipitate and 

 felt were transferred and stirred, after which the crucible was also put into the solu- 

 tion, since particles of the precipitate stick persistently to its sides. After the oxida- 

 tion had proceeded five or six minutes manganese hydroxid separated out and the 



J.Chem. Soc., 77:1076. 



bAmer. J. ScL, 24: 433; Chem. News, 97: 124. 



