Austiii — Do'iible Aminoniuin Phosphates in Analysis. 159 



used, but makes no mention of the exact strength of the 

 alcohol employed in his work. 



In order to test the insolubility of ammonium phosphate in 

 alcoholic washing I have made various experiments, the details 

 of some of which are given in the following account. Portions 

 of a solution of manganous chloride, standardized as the sul- 

 phate according to the method^ described in a former paper, 

 were carefully measured from a burette, ammonium chloride 

 and microcosmic salt were added in the proportions formerly 

 recommended, and precipitation of the ammonium manganese 

 phosphate was completed exactly as directed. After cooling, 

 the precipitates were collected on asbestos under pressure in a 

 perforated platinum crucible. In the experiments the results 

 of which are given under A of the table, the precipitate was 

 in each case washed with distilled water made faintly ammoni- 

 acal, while in those recorded under B, C, and D of the table 

 the precipitate was washed with two hundred cubic centi- 

 meters of a one per cent ammonium phosphate solution, and 

 rinsed with forty cubic centimeters of alcohol of different 

 strengths, — sixty, eighty and eighty-eight per cent, — applied 

 in successive portions. 



correspond- 

 ing to 

 MnCU 

 taken. 



Washed with 



ammoniaeal 



water. 



A 



Washed with 



1^H(NH4)2P04 



rinsed with 



60/. alcohol. 



B 



Washed with 



1^H(NH,).P04 



rinsed with 



80,^^ alcohol. 



C 



Washed with 



1^H(NH4)4P04 



rinsed with 

 88^ alcohol. 

 D 



grm. 



grm. 



grm. 



grm. 



grm. 



0-3020 



0-3042 



0-3050 



0-3058 



0-3066 





0-3020 



0-3041 



0-3074 



0-3086 



From these experiments it appears that the procedure 

 involving the washing of a precipitate of ammonium manga- 

 nese phosphate by a one per cent solution of ammonium phos- 

 phate, draining with the pump, and then completing the 

 washing with alcohol, results in a contamination of the pre- 

 cipitate proportionate to the strength of the alcohol used. 

 Even the thin felt of asbestos alone when washed with 

 ammonium phosphate followed by alcohol retains amounts of 



Weight of 

 asbestos felt. 



grm. 

 0-0681 



Weight of asbestos 

 felt after washing 

 ten times with a 

 1% solution of am- 

 monium phosphate 

 and rinsing with 

 distilled water. 



grm. 

 0-0681 



Weight of asbestos felt after washing 

 with a 1% solution of ammonium 

 phosphate and rinsing with alcohol 

 of the strength given. 

 60^ 80^ 88^ 



grm. grm. grm. 



0-0682 0-0684 0*0686 



* This Journal, v, 309. 



