4S0 
CARBOLIC OR PHENIC ACID AND ITS PROPERTIES. 
Lastly, there remains in the still (after the heavy oils and semi-solid substances have 
distilled off) a product, which is fluid at the high temperature at which this operation is 
conducted, but which, when exposed to the natural temperature of the atmosphere, be¬ 
comes hard and brittle, and is known under the name of pitch, and which is so largely 
employed in Paris under the name of asphalte, bitumen, etc., to form the foot pave¬ 
ments and public walks, as well as for the manufacture of a sort of concrete, called in 
England patent fuel. 
I now come to carbolic acid. 
It is twenty years since Laurent, the eminent chemist, first pointed out the easy me¬ 
thod of extracting carbolic acid from coal tar. It consisted in submitting the light oils 
to a fractional distillation, and then treating with a concentrated solution of potash 
those products which distilled at a temperature between 160 and 200 degrees, separating 
the alkaline solution from the hydrocarbons which floated on it, and then neutralizing 
by an acid which liberated the carbolic acid. 
Such was Laurent’s method of preparing carbolic or phenic acid, but pure carbolic 
acid was only there in a very small proportion; it was, in fact, a mixture composed 
chiefly of different liquids similar in properties and composition to carbolic acid, and 
though Laurent succeeded in obtaining pure carbolic acid, still the process devised by 
him was too expensive to answer as a commercial production ; and besides, his method 
of operating was too complicated. 
In 1847, Mansfield, and towards 1856, M. Bobceuf, made known processes which, in 
fact, were only a modification of Laurent’s, for they consisted principally in employing 
caustic soda instead of potash, and in treating the whole of the light oils, instead of a 
special portion, as Laurent had done ; but by these processes a very impure acid was 
still obtained, from which it was very difficult, as experience has shown us, to extract 
pure carbolic acid; however, in a commercial point of view, the process of these gentle¬ 
men was a step in advance. I may add, that it was this impure carbolic acid which 
Mr. John Bethell manufactured, at my request, about the year 1847; and it was this 
impure acid which was also employed by several chemists who, like myself, studied the 
properties of this substance, and who endeavoured to apply it usefully, either in the 
production of picric acid, or in preventing the transformation of tannic acid into gallic 
acid, in tanning substances, or, finally, in the preservation of subjects for the dissecting- 
room. M. Boboeuf also made use of it in preserving organic bodies from putrefaction, 
a property which has received of late very important applications. 
In 1859, M. Marnas, of the firm of Guinon, Marnas, and Bonnet, of Lyons, came to 
Manchester, and asked me to furnish him with a purer carbolic acid than had been as 
yet manufactured. He showed me a white and crystalline product, which he gave as a 
specimen. It was then necessary to make new experiments, and I discovered that the 
best mode of preparation was not by treating light or heavy oils of tar with concen¬ 
trated alkalies, but, on the contrary, treating the impure benzines of commerce or naph¬ 
thas with weak alkaline solutions. By this means a semi-fluid, blackish product was 
obtained, a little heavier than water, of a density of 1'06, and which contained 50 per 
cent, of real carbolic acid, which acid I managed to separate in part by careful distilla¬ 
tion. It is this product which was employed by Messrs. Guinon, Marnas, and Bonnet, 
and others, till 1861, for the manufacture of colours derived from carbolic acid. At this 
period the colours obtained from aniline were so fine and brilliant that, to keep up a 
comparison with them, it was necessary to improve those derived from carbolic acid. 
To effect this it was necessary to improve the quality of the carbolic acid then manu¬ 
factured, and, after some trials, we (F. C. Calvert and Co.) produced carbolic acid 
in white detached crystals, melting at between 26 and 27 degrees, and I may here add 
that this is the product which is now generally employed in commerce and industry, for 
there are numerous examples of it at the present Universal Exhibition. In 1863 this 
relative purity was not sufficient. The same firm which had requested the improve¬ 
ments which I have before named asked us to try and make it still purer. We again 
set to work, and produced commercially Laurent’s carbolic acid; that is to say, a sub¬ 
stance melting at 34 degrees Centigrade, and boiling exactly at 186 degrees. This be¬ 
came a very important commercial product for us, and we delivered large quantities 
monthly. 
From this time I made many efforts to draw the attention of medical men to the 
really remarkable therapeutic properties of carbolic acid, but the tarry and sulphurous 
