THE PRODUCTS OF THE DISTILLATION OF COAL. 293 



means of machinery (that used in America was the motive-power of a 

 descending weight) through a vessel of the hydro -carbon, kept slightly 

 warm to assist evaporation ; the air saturated with the vapour is then 

 burnt as gas. It is by no means probable that this light will, as it is 

 stated, supersede coal gas, for below a certain temperature the air will 

 not carry sufficient vapour to furnish a good light, and in cold weather 

 the benzole condenses in the pipes, and the liquid itself requires the 

 application of heat. 



Inspired in a state of vapour benzole possesses anaesthetic properties, 

 and, like chloroform, produces insensibility to pain ; but it has not 

 come into general use for this purpose, unpleasant symptoms having 

 displayed themselves on several occasions in those who have taken it. 

 It has been employed medically with success as an external application 

 in some affections of the skin ; for itch I have found benzole an effectual 

 and speedy remedy. 



On many occasions and for many reasons the detection of benzole is 

 frequently a matter of importance. Dr. Hofmann has furnished us with 

 a ready method of detecting it. The liquid to be examined is warmed 

 in a test-tube with fuming nitric acid, it is then diluted with water, 

 and shaken up with ether, which dissolves the nitro-benzole formed. 

 The ethereal solution is separated by a pipette and mixed with an equal 

 volume of alcohol and hydrochloric acid, and granulated zinc is then 

 added. After five minutes the mixture is saturated with potass and 

 shaken up with ether and the ethereal solution being evaporated on a 

 watch-glass, the addition of a drop of a solution of chloride of lime 

 strikes the purple colour indicative of aniline. 



Carbolic Acid (C 12 H 5 0, H 0), called also Phenol and Phenylic 

 acid is another important product of the distillation of coal. When 

 those portions of the acid of coal-tar which distil between 300° and 

 400° are mixed with a hot solution of potash, a crystalline mass results, 

 which is resolved by water into a light oil and heavy alkaline liquid, 

 when the latter is neutralized by hydrochloric acid, the impure carbolic 

 acid separates as a light oil. This is purified by the action of chloride 

 of calcium and distillation, exposed to a low temperature, and the 

 crystals formed drained from the mother liquor and carefully preserved 

 from air. The crystals are colourless and deliquescent, fuse at 95° and 

 pass into vapour at 370° Carbolic acid has an odour of creosote, in fact 

 a great deal of the creosote met with in commerce is only carbolic acid 

 more or less impure. It is one great cause of the offensive odour of 

 some coal oils. 



The disinfecting power of coal-tar has long been known, a property 

 which is due to the carbolic acid. It belongs to that class of colytics 

 known as antiseptics, whose action is to prevent putrefaction by arrest- 

 ing it in a singular way, without destroying the organic matter, but at 

 the same time do not allow decay to go on. Injected into the bodies 

 of animals, it preserves them unaltered in contact with the air, and 



