Sulphate and Dichromate. 295 



Formation of Mixed Crystals of Ag^SO A and Ag 2 Cr % 0. at 25°. 





Analysis of 25 cc of solution 



Molecular ratio 



Acidity 



equiv. 



per 



liter 







Ag. S0 4 



Na 2 S 2 3 <> 

 Cr 2 0, 



Solution 



Crystals 



Solid phase 



grin. grin. 



cc. grm. 



S0 4 



Cr 2 7 



S0 4 



Cr 2 7 





I 01621 0-3690 







100-0 



o-o 



100-0 



o-o 



2476 



Ag 2 S0 4 



II 0-1645 



0-3693 



2-41 



0-0074 



99-10 



0-90 



98-8 



1-2 



0-2496 



Mixed crystals 



III 0-1621 



0-3666 



2-41 



0-0074 



99-09 



0-91 



• 



95-9 



4-1 



0-2484 



Mixed crystals 

 (trace of Ag 2 Cr 2 7 ) 



IV 0-1612 i 0-3666 



223 



0-0068 



99-2 



0-8 



84-5 



15-5 



0-2482 



Mixed crystals 



+ Ag 2 Cr 2 7 



V 0*1630 0-3617 



2-46 



0-0076 



99-0 



1-0 



o-o 



1000 



0-2440 



Ag 2 Cr 2 7 



VI 0-1381 0-3476 



3-00 



0-0093 



98-8 



1-2 



o-o 



100 



0-2420 



Ag 2 Cr 3 7 



1 

 VII -0583 



7-13 



0-0230 



96-7* 



3-4* 



o-o 



100-0 





Ag 2 Cr 2 7 



* Calculated from the average acidity. 



scarlet in III. With the scarlet crystals produced in experi- 

 ment III was mingled a minute quantity of much darker 

 crystals. These were again obtained in experiment IV in 

 large amount, together with mixed crystals of the same scarlet 

 color as before. The three remaining experiments gave crys- 

 tals in which no sulphate could be detected, and which, on 

 complete analysis, were* found to be pure silver dichromate. 

 The color of these crystals, deep wine red by transmitted light, 

 metallic gray by reflected light, was the same as that of the 

 darker crystals obtained in experiments III and IV. With 

 much labor about 15 milligrams of the latter crystals were 

 separated under the microscope from the scarlet crystals with 

 which they were mingled, and were carefully tested for sul- 

 phate without result, thus showing that they too consisted of 

 pure silver dichromate. 



The mixed crystals, as proved by the usual goniometric and 

 optical tests, were orthorhombic, having the same pyramidal 

 habit and nearly the same crystal angles as those given by 



