METHOD OF PREPARING CHROMIC ACID, ETC. 199 
reaction with starch and sulphuric acid is still perceptible. 
I only obtained distinct evidence of iodine in the mother- 
leys from the salt works of Halle ; in all the others none, or 
so very slight, that the presene of iodine cannot be asserted 
positively. — Chem, Gaz.from Journ.fur Prakt. Chem. 
ART. XXXIX. — ON AN ADVANTAGEOUS METHOD OF PRE- 
PARING CHROMIC ACID, AND ON A PECULIAR BEHAVIOUR 
OF THIS ACID TOWARDS SULPHURIC ACID. 
By Dr. P. A. Bolley. 
The process described by Fritzsche for preparing chromic 
acid from a hot solution of the bichromate of potash by 
means of sulphuric acid, is decidedly preferable to every 
other on account of the large produce. Warington and 
Bottger have modified this process, because the product 
obtained according to Fritzsche's method is not pure, but 
always contains some sulphate of potash; they recommend 
mixing a cold saturated solution of the bichromate of pot- 
ash with 1 or U parts of monohydrated sulphuric acid. 
The proportion of the sulphuric acid to the bichromate of 
potash is not stated by Fritzsche ; the amount of acid pres- 
cribed by Warington and Bottger is so remarkably great and 
renders the product so dear, that it is worth while endea- 
vouring to find a process requiring less sulphuric acid. 
When 12 to 15 parts by measure of sulphuric acid are 
prescribed for 10 parts of the solution of the salt saturated 
at the ordinary temperature, this large amount has cer- 
tainly some other part to act than the decomposition of the 
salt, viz. the precipitation of the eliminated chromic acid 
from its aqueous solution. I endeavoured to separate the 
