502 



•\*^M«SBr84 Playfair «wf/ Joule on '^'^ 



dissolved in 1000 grains measure of a dilute solution of mu- 

 riatic acid, gave an increase of 15*7 in two experiments at 57° ; 

 this result makes the volume of an equivalent in solution 

 62'8. ^'^-^! ■•.ij.>jxl 



The mean of various experiments on Ihis salt gave'dtf 'it34 

 crease of 18*15 on immersing the above quantity of salt in 

 turpentine, which yields 72*6 as the volume of the equivalent, 

 and 2*466 as the specific gravity of the salt. - 



The results now described show that the chromates fortti'a* 

 group different from the classes of salts hitherto given, i-* ■-'^^^ 



'it)TAB;^E X,^ — Showing the Volumes occupied by cert^j%. gj 



-u.jjq jju 0f xisiiiaq Chromates. i^; ^fljij^joq 



Designation. 



Volume of salt 

 in solution. 



Volume of salt. 



'i i .f 

 ["■"170 8? 



Name. 





Chromic acid 



Chromate of potash 



Sesquichromate of potash. 



Bichromate of potash 



Terchromate of potash . . . 



Bichromate of chloride 1 



of potassium J 



Formula. 



CrOs 



KO, CrOg 



2K0, SCrOa 



KO, 2Cr03 



KO, SCrOg 



KCl + 2Cr03 



.38 



a s 



> 



52-19 



99-50 



251-07 



151-70 



203-92 



179-08 



) / 1 2 



18-0 

 17-9 

 720 

 45-3 

 71-9 



62*8 



18-0 



18-0 



720 



45 



72 



19-5 

 371 



94-8 



57-8 

 76-8 



.63 I 72-6 



jtfitfi n.trn. 



I 



2-676 

 2-682 

 2-648 

 2-624 

 2-655 



2466 



An inspection of the previous table will show clearly that 

 the chromates differ from the salts described in the former 

 sections. In the volumes in solution there is no difference j i 

 they are multiples of 9, and follow the usual law of the sum" 

 of the volumes, being made up of the volumes of the consti- 

 tuents of the salt. Chromate of potash possesses two volumes 

 in solution, exactly as is the case with its analogue sulphate of 

 potash. The latter salt affects three volumes in the solid state, 

 and so naturally should chromate of potash. In bichromate 

 of potash we see these three volumes appearing in solution, 

 united to two volumes possessed by the chromic acid attached 

 to the chromate of potash ; in sesquichromate of potash they 

 again reappear, and so also in terchromate of potash. The 

 fact that the number of volumes possessed in the solid state 

 by the lowest member of a series of salts passes over into the 

 higher members when in solution, finds examples in the car- 

 bonates and oxalates, and is not peculiar to the chromates. 



The solid volumes of the chromates possess decided peculi- 

 arities, being neither multiples of 1 1 nor of 9'&. Chromic acid 



