CARBOLIC ACID 719 



more than 50 per cent, of acids soluble in strong solution of potash. The insoluble 

 portion contains naphthaline, fluid hydrocarbons, and small portions of chinoline and 

 lepidine. Carbolic acid, when very pure and dry, is quite solid and colourless. The 

 crystals often remain solid up to 95, but a trace of -water renders them fluid. Its 

 specific -gravity is 1*065. Carbolic acid, when mixed with lime and exposed to the air, 

 yields rosolic acid. The lime acquires a rich red colour, during the formation of the 

 acid. No means of dyeing reds permanently with this substance have yet been made 

 known. Unfortunately, the red tint appears to require an excess of base to enable it 

 to exist, consequently the carbonic acid of the air destroys the colour (Dr. Angus 

 Smith). I find that homologues of carbolic acid exist which boil at a temperature 

 beyond the range of the mercurial thermometer, and that all the acids above carbolic 

 acid afford rosolic acid, or homologues of it, when treated with lime. Creosote of 

 commerce appears to consist of a mixture of carbolic and cresylic acids. If only that 

 portion be received which distils at the temperature given by Reichenbach as the 

 boiling point of creosote, it will, if prepared from coal-oil, consist almost entirely of 

 cresylic acid ( Williamson and Fairlie). A splinter of deal wood, if dipped first in carbolic 

 acid and then in moderately strong nitric acid, acquires a blue tint. For a comparison 

 of the properties of Creosote and Carbolic Acid, see CBEOSOTE. C. G. "W. 



More than five-and-twenty years ago, Laurent extracted carbolic acid from coal-tar 

 by fractional distillation, as described above ; the products of distillation were treated 

 with caustic potash and the alkaline solution then neutralised by an acid so as to 

 liberate the carbolic acid. This process was modified in 1847 by Mansfield, and in 

 1856 by Baboeuf ; these chemists substituted caustic soda for the potash, and worked 

 upon all the light oils, instead of confining themselves to a portion only, as Laurent 

 had previously done. Still the acid obtained by these methods was very impure, and 

 it remained for the late Dr. F. Crace-Calvert to introduce successive improvements into 

 the manufacture until he finally obtained a pure product. In 1859 Calvert proposed to 

 work upon the impure benzines or naphthas of commerce ; these he treated with weak 

 alkaline solutions, and thus obtained a product which was rich in carbolic 'acid 

 containing as much as 60 per cent, and capable of yielding a great part of this acid 

 on distillation. By further modifications of his process, he succeeded in obtaining a 

 pure hydrate of carbolic acid (mono-hydrate of phenol) of the composition C i2 H s 2 

 HO [2 (C 6 H S O) H 2 O], The tarry and sulphurous .odours, which clung to the earlier 

 forms of carbolic acid, and were so prejudicial to its use for many purposes, have been 

 entirely removed in some of Calvert's later preparations. In addition to the ordinary 

 form of the acid, Messrs. Calvert and Co. now prepare carbolic-acid powder and 

 carbolic-acid soap. 



On an industrial scale, carbolic acid, or phenol, was first produced by the late Dr. 

 Ernest Sell, a German chemical manufacturer, distinguished for his scientific attain- 

 ments and predilections. Dr. Sell introduced the use of phenol as a substitute for the 

 ever-varying creosote. The claims to chemical individuality of the latter substance, 

 notwithstanding numerous investigations to which it has been submitted, are by no 

 means finally established ; many chemists, in fact, considering creosote as a mixture 

 of phenol with larger or smaller quantities of its homologues, cresol and phlorol. 

 The manufacture of coal-tar-derived creosote was extensively carried on by Dr. Sell 

 in his factory at Offenbach-on-the-Main ; and Dr. Hofmann saw, nearly twenty years 

 ago, at that factory, hundredweights of phenol as white and beautifully crystallised 

 as the specimens exhibited in London in 1862. 



Of late years, carbolic acid has obtained extensive application as an antiseptic and 

 disinfectant. Its volatility gives it the advantage of being very rapidly diffused 

 through an infected atmosphere. During the cattle-plague it was employed with 

 great success by Mr. Crookes. Carbolic acid is also used in surgery for dressing 

 offensive wounds, and as an application in certain forms of skin-disease. But the 

 most interesting use of phenol is to be found in the manufacture of certain dye-stuffs 

 from this acid and its derivatives. The following are the more important of these 

 carbolic-acid dyes : 



YELLOW DYES: Picric acid, Carbazotic acid, or Trinitrophenylic acid. Though 

 originally discovered by Welter, the composition of this body was not properly 

 understood until Laurent examined it in 1841. It is obtained by the action of nitric 

 acid on carbolic acid, or on phenyl-sulphate of soda. As far back as 1847, it was 

 used for dyeing by Messrs. Guinon, of Lyons. It is employed for imparting a yellow 

 colour to silk and wool ; and also as a green dye when associated with indigo and blue 

 colouring matters. Picrate of soda has been substituted for the pure acid, but this 

 salt is dangerously explosive. Sea PICRIC Aero. 



Aurinor Yellow Coralline. In 1861 Kolbe and Schmidt first obtained this compound 

 by heating carbolic acid with oxalic acid and concentrated sulphuric acid. Commercial 

 aurin is a brittle resinous substance, having the colour and lustre of cantharides, and 



