508K .\v^M€ssrs. Playfair flms? JowletwwwNK 



miiltiplesidf'9;8>:ni the double cWorid€s,'iartd['<tfMii present© 

 the same number for its solid volume as chloride of potassium. 

 The isomorphism of potassium and sodium is so entirely hy- 

 pothetical, that it will not excite surprise to find the volumes 

 of the chlorides so different. We were less prepared to detect^ 

 the difference between iodide and chloride of potassium ; but) 

 have confirmed it by an examination of iodide of ammonium j[ 

 50 grains of which dissolved in 1000 of water with an increase* 



^nBiffl^^^P^ gives -— - = six volumes for the equivalent, a, 



r6^i!ilt- Confirmatory of our determination of five volumes foi*^ 

 iodide of potassium ; the increase of one volume being in'^ 

 conformity with the usual behaviour of ammoniacal salts.!' 

 We shall return to the consideration of the chlorides in a fti-' 

 ture section. , . , ■' "^ 



nn io diiuo't 9fii gnioiiiq ^ajnararwqxa zig 1o iiBum ariT 

 io 08B9*ioni m; saw ^sah^^t^j^^-^'r^f^ain'i-g tt'SO .ixialxsviupa 



bnu ^ia^lnnupo srlcf 'io 9( ' gfi S'^Q 89/ig doiriw «lt*£S 



-• Chromatesi-r - ^;4:.~ -, -.^f^ p^. p.-vo 



The 6hromates present a class of salts which offer some 

 peculiarities with regard to their volumes, in elucidating which 

 we had occasion to repeat our experiments very often, and, 

 therefore, give the mean of the results, instead of taking up' 

 unnecessary space in the Transactions of the Society by de- 

 scribing each experiment individually. 



Chromic Acid, Cr03 = 52*19. — The chromic acid used in 

 our experiments was obtained by adding sulphuric acid to bi- 

 chromate of potash. It was in beautiful distinct crystals of^ 

 nearly a quarter of an inch in length, being the finest and 

 purest specimen which we have obtained in many prepara- 

 tions of this acid. 



The half of an equivalent, 26*09 grains, dissolved in 1000 

 of water with an increase of 9'0 at 72° j this gives 1 8*0 as the 

 volume of chromic acid in solution. 



The same quantity of acid, thrown into the solution from 

 which it had crystalhzed, gave an increase of 9*7 and 9*8 in, 

 two experiments. .<^^^^o^ m inoi 



I. Chromic acid, volume 19*4 ,.. 2*690 ./] ^f g.gf 

 II. ... ... , ,19"6,, ,.. 2-663 



!f!^: Mean'^'^^'^.'^W^^V: ¥676 



Yellow Chromate of Potash, KO, CrOs=99-50.— On dis- 

 solving 50 grains of this salt in 1000 grains of water, the in- 

 crease was 9*0 at a temperature of 58°; this gives 17*9 as 

 the volume of the equivalent in solution. 



The mean result of ten experiments, on immersing 49*75 



