On the Bichromate of the Perchloride of Chrome, 433 



The lowest heat of a spirit-lamp is quite sufficient for effect- 

 ing the decomposition. 



So far as I have been able to observe, there are no differ- 

 ences in the phaenomena exhibited in the reduction of Hg 

 from Hg CI and Hg Cl^, or in any of the circumstances con- 

 nected with the processes, by which we can form any judge- 

 ment as to which of these compounds we are operating upon. 

 I am. Gentlemen, yours, &c. 



Leeds, June 5, 1838. John B. Nevins. 



LVIir. On the Process for obtaining the Bichromate of the 

 Perchloride of Chrome, as viewed under the Microscope. 

 By the Rev.. Edwakd Craig, F.R.S.E. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



T OBSERVE in your Number for July, p. 78, a notice of 

 the bichromate of perchloride of chromium, and of the 

 process for obtaining it. It may perhaps be interesting to 

 call attention to the exhibition of this process under the mi- 

 croscope, which certainly throws some light upon the action 

 going on. It presents one of the most beautiful objects ever 

 seen. 



Put a very small portion of the muriate of soda on a thin 

 flat glass, and add to it a drop of sti'ong solution of bichromate 

 of potass; lay this on the port-object, and adjust it to the 

 focus of the microscope. Then place upon another flat glass 

 a drop of sulphuric acid, and turn it down upon the other 

 glass. The action commences. The sulphuric acid is seen 

 attacking and breaking down the muriate of soda and setting 

 free the muriatic acid. Crystals of sulphate of soda are speedi- 

 ly formed. The sulphuric acid acts also on the bichromate 

 of potass, and sets free the chromic acid ; crystals of sul- 

 phate of potass are also formed. Over these crystals of both 

 kinds a multitude of green particles are observed, which are 

 })robably a chromate of potass, formed from one equivalent of 

 the chrome in the bichromate, and then the other equivalent 

 of the chrome combines with the disengaged chlorine, and 

 appears in large blood-red globules over the whole field. The 

 operation when steadily watched is very beautiful; and it is 

 one in which the microscope seems to develope with peculiar 

 interest a process whose specific features are lost sight of in 

 the retort. According to the view which is thus given of the 

 process, it seems natural to call the product chlorochromic 

 acid. I am. Gentlemen, yours, &c. 



Burton Latimer, Kettering, Oct, 20, 1838. EdWARD Craig. 



Phil. Mag. S. 3. Vol. 13. No. 84. Dec. 1838. 2 F 



