242 Gooch and Bosworth — Silver as the Chromate. 



below two or three milligrams for volumes approximating a 

 hundred cubic centimeters. Solution of the first precipitate 

 in ammonia and reprecipitation by boiling to low volume to 

 remove the excess of ammonia failed to overcome entirely the 

 solubility of the silver salt, which appears to be due to a tend- 

 ency on the part of the ammonium chromate to pass to the 

 condition of dichromate with loss of ammonia from the boiling 

 solution. 



In the next experiments, therefore, potassium chromate was 

 used as the precipitant. In Table I, A are given the details 

 of experiments in which an excess of potassium chromate was 

 added to silver nitrate, the solution boiled, the precipitate 

 transferred to the asbestos filter in a perforated crucible 

 by means of a dilute solution of potassium chromate and 

 washed with small portions of water, and the residue after 

 drying with gentle heat weighed as silver chromate. In these 









Table I. 







Silver 

 taken as 



AgN0 3 



K 2 Cr0 4 Ag 2 Cr0 4 

 used weighed 



Silver 

 found 



Error 

 in terms 

 of silver 



Volume 

 of solu- 

 tion 



Weight 



of 

 silver 



Volume 

 of solu- 

 tion 



Weight 







cm 3 . 



grm. 



cm 3 . 



grm. grm. 

 A 

 ipitation by K 2 Cr0 4 . 



grm. 



grm. 







Prec 







15 



0-1652 



50 



0-3 0-2536 



0-1649 



— 0003 



10 



o-noi 



50 



0-3 0-1693 



0-1101 



o-oooo 



25 



0-1437 



50 



0*3 0-2200 



0-1436 



—o-oooi 



25 



0-1437 



50 



0-3 0-2210 



0-1437 



o-oooo 



Precipitat 



JD 



ion by K 2 CrOi, treatment with NHiOHan 



id evaporation to dryness. 



25 



0-1348 



50 



0-3 0.2077 



0-1351 



+ 0-0003 



30 



0-1618 



50 



0-3 0-2500 



0-1626 



+ 0-0008 



30 



0-1618 



50 



0-3 0-2520 



0-1639 



+ 0-0021 



Precipitat 



ion by K 2 CrOi, treatment with NH±OH and boiling to 



10-15 cmZ . 



a volume of 



25 



0-1576 



50 



03 0-2422 



0-1575 



—o-oooi 



25 



0-1576 



50 



0-3 0-2414 



0-1570 



— 0-0006 



50 



0-3152 



50 



0-3 0-4852 



0-3155 



+ 0-0003 



50 



0-3152 



50 



0-3 0-4843 



0-3149 



— 0*0003 



50 



0-3152 



50 



0-3 0*4847 



0-3152 



o-oooo 



D 



Precipitation by K 2 CrO iy treatment with NHiOH and boiling to a volume of 

 10—15 cmZ in presence of 1 grm. of sodium nitrate. 



10 0-1101 50 0-3 0-1693 O'llOl 0*0000 

 15 0-1652 50 0-3 0*2536 0-1649 — 0'0003 



