Morris—The Preparation of Selenic Acid 
369 
THE PREPARATION OF SELENIC ACID 
H. H. Morris 
Selenic acid was first prepared by Mitsclierlich in 1827d 
He decomposed lead selenate suspended in water, by hydrogen 
sulfide. In 1830 Berzelius^ suggested the oxidation of an al¬ 
kali selenite by means of chlorine, for the preparation of selenic 
acid. In 1834^ Ballard used hypochlorous acid for the oxida¬ 
tion. In 1840, Rose^ suspended selenium in Avater and passed 
in chlorine which oxidized it to selenic acid. WohhvilP in 1860 
used potassium dichromate, lead dioxide, and manganese di¬ 
oxide as oxidizing agents in the preparation of the acid. In 
the same year von Hauer® prepared selenic acid by the decomp¬ 
osition of cadmium selenate with hydrogen sulfide. Nine years 
later Thomsen^^made what was claimed to be very pure sel¬ 
enic acid by treatment of silver selenite with bromine. 
Thomsen took no steps to remove any selenious acid Avhich 
might be present, and from the present work it seems that his 
preparation could not have been quite pure. 
Von Gerichten,® working in 1873, used a method very similar 
to that of Mitscherlich. In 1899 Cammeron and Macallan^ 
published their work on the concentration of selenic acid and 
showed that it could be obtained in the anhydrous condition. 
They constructed tables of the specific gravity and percentage 
strength of the acid, which were very good for the range cov¬ 
ered, but which were later made complete by the Avork of Len- 
her and Diemer.^® 
1 Ann Ph Ch Pogg 9, 623. 
2 Berzelius Lehrbuch Bd III, s 16 der 4ten deutschen Auflage. 
3 Ann Ph Ch Fogg 57 , 225. 
^Ann Ph Ch Pogg, 45, 337. 
3 Ann Chem Pharm Lieb 114, 169. 
® Sitz Akad AVein 39 , 399. 
^Ber 2, 598. 
3 Ann Chem Pharm Lieb, 168, 214. 
»C N 59 , 219 232, 258, 267. 
^“Jr Phsic Chem 13, 505. 
24—S. A. L. 
