468 
DR. JOHN STENHOUSE ON THE OILS PRODUCED BY THE ACTION 
M. Cahours also found that when thiofurfurol is distilled it is entirely decomposed, 
producing a beautifully crystalline substance containing no sulphur. Its formula is 
Cjg Hg O 4 , or some multiple of these numbers. 
As furfurol, both from its composition and properties, occupies a somewhat isolated 
position in regard to other essential oils, it appeared to me not improbable that it 
would be found on more extended investigation not to stand really alone in nature, 
but to be one of a series of similar oils. This consideration induced me about six 
months ago to resume its examination, and, as will presently be seen, the expectation 
I had formed was not altogether without foundation. Before detailing these re- 
searches, however, I shall shortly state a few additional observations which I have 
recently made upon furfurol and some of its compounds. 
Furfurol is most advantageously prepared by distilling one part of bran with rather 
more than half its weight of sulphuric acid diluted with two parts of water. I find, 
however, that furfurol may be also produced with muriatic acid, though in practice it 
is more advantageous to employ sulphuric acid, as it remains in the retort and does 
not distil over with the oil, as is the case with muriatic acid. 
The arrangement for preparing furfurol on a considerable scale which 1 have found 
most suitable, is the following. About 32 lbs. of wheaten bran and 20 lbs. of sul- 
phuric acid diluted with twice its bulk of water, were introduced into a large three- 
necked WouLp’s-bottle made of salt-glazed earthenware. These bottles are usually 
employed as condensers in the manufacture of muriatic and nitric acids, and are ca- 
pable of containing from twenty to thirty gallons each. A leaden pipe connected 
with a tolerably large steam-boiler is passed through a perforated cork to near the 
bottom of the stone-ware bottle, from the top of which, on the opposite side, a second 
pipe is carried into the worm of a condensing apparatus, which is kept cool by means 
of a plentiful supply of cold water. The steam from the boiler is then passed through 
the mixture of the acid and the bran, which soon becomes hot and then boils, when 
a weak aqueous solution of furfurol passes over into the condensing apparatus and is 
collected in the usual way; the whole of the oil usually comes over in from 16 to 
18 hours. This weak liquid is pretty strongly acid, and requires to be exactly neu- 
tralized with pounded chalk, and to be rectified till about the half of it has distilled 
over. It is important to avoid adding an excess of chalk, and rather to leave the 
liquid slightly acid, as an excess of chalk sets free the ammonia present in the solution, 
which, combining with the furfurol, oxidizes it, and thus greatly diminishes the amount 
which would otherwise be obtained. The first portion only of the liquid which distils 
over is preserved, as that which remains in the still contains scarcely any oil. The 
now somewhat stronger solution of the oil is then supersaturated with common salt 
and again cautiously rectified. The first portions of the liquid which come over yield 
a considerable amount of oil, and by repeatedly saturating the weaker solutions with 
salt and rectifying, the whole of the oil they contain may be pretty readily obtained. 
The 32 lbs. of bran yielded from 12 to 13 ozs. of furfurol. I have invariably found 
