1835.] of the Distillation of Pit Coal. 53 



which after rectification, appears as a thick liquid, con- 

 sisting of pure anhydrous carbolic acid. When the lead 

 salt is not properly dried, water passes over with the acid. 

 This process is necessary to free it from the heterogeneous 

 compounds in the coal-tar, which are ammonia, cyanol, 

 pyrrol, and leucol. These are removed by the boiling. 

 Creosote and sulphur are partly precipitated by the lead, 

 and the rosolic and brunolic acids remain in the retort, 

 while the water is separated by rectification. 



Separation of Rosolic and Brunolic Acid. 

 The residue in the retort, after the last process, is to be 

 boiled with water, dissolved in spirits, and mixed with 

 lime-water. A rose coloured solution of rosolate of lime is 

 formed, and brunolate of lime remains at the bottom, as a 

 brown precipitate. From the rosolate of lime the rosolic 

 acid is separated by acetic acid, and again combined with 

 lime, whereby brunolic acid separates. The decomposition, 

 by means of acid and repeated solution, should be continued 

 as long as brunolic acid is observed. The rosolic acid is 

 then collected on a filter, and dissolved after edulcoration 

 and drying in alcohol. There remains on evaporation, 

 a vitreous, hard, orange-coloured mass. The rosolic acid 

 may also be separated by evaporating the solution of roso- 

 late of lime to the thickness of syrup, and mixing it with 

 J spirits. In the course of a day red crystals of the salt 

 appear on the sides of the glass, which are to be removed, 

 well washed, dissolved in water, evaporated, and treated 

 with acetic acid and lime-water. The brunolic acid is se- 

 parated from the brunolate of lime by digestion with an 

 excess of muriatic acid. The brunolic acid separates in 

 brown flakes, which for complete separation from the 

 rosolic acid, must be repeatedly treated with lime and acid. 

 The acids separated from the lime by muriatic acid, are 

 dissolved in soda ley, and the solution is mixed again with 

 muriatic acid, when a pure precipitate of brunolic acid 

 falls, which may be completely purified by solution in 

 alcohol. * 



* Reichenberg.(Schweigg. Journ. lxix. 19) has drawn the following conclusions 

 with regard to pit coal 1 — L__of an ethereal oil is procured by distillation, with 

 water which is identical with petroleum. 2. Petroleum is not a product of the 



