PREPARATION OF ANHYDROUS SULPHURIC ACID. 3l3 
ART. LXV.— PREPARATION OF ANHYDROUS SULPHURIC 
ACID. 
By Mr. H. Sugden Evans. 
The process we find described in most chemical works, 
for the preparation of anhydrous sulphuric acid, consists in 
submitting Nordhausen oil of vitriol to distillation at a low 
temperature, with a suitable apparatus for condensing the 
white fumes which pass ov^r. Owing, however, to the 
difficulty of procuring, in this country, good Nordhausen 
oil of vitriol, containing any appreciable quantity of the 
anhydrous acid, this process has failed in the hands of many 
who have tried it, and the|substance under notice is generally 
looked upon as a rare chemical product. In its crystalline 
state, it is so beautiful an object, that many chemists would, 
no doubt, be anxious to add it to their collection of chemi- 
cal specimens, if they knew of an easy process by which to 
prepare it. 
Some years ago Doebereiner and Magnus described a 
process for its preparation, which consisted in passing a 
mixture of dry sulphurous acid and oxygen gases through 
a tube filled with spongy platinum and heated to about 
572° Fahr.; but this process requires a somewhat complicat 
ed apparatus, and would not be very easy of execution by 
an amateur manufacturer. 
More recently a notice was published in the Comptes 
Rendus, of a process suggested by M. Ch. Barreswil, for 
obtaining it by means of anhydrous phosphoric acid. I have 
tried this process, and have found it to be neither difficult 
nor expensive. The process was not very minutely de- 
scribed in the notice of it above alluded to, and therefore 
as the result I have obtained has been perfectly satisfactory, 
