THE PRODUCTS OF THE DISTILLATION OP COAL. 295 



stacle was the impossibility of fixing it to constitute a fast colour. 

 Lately these difficulties have been overcome by Guinon, who by combin- 

 ing this substance with ammonia, has produced a beautiful permanent dye, 

 used largely for printing muslins, and known under the name of peonine. 

 That the introduction of nitrogen in this manner endows non-azotised 

 vegetable substances with a power of fixation, and likens them in this 

 respect to animal substances, is a highly interesting scientific fact. The 

 yellow dye afforded by carbolic acid is the result of the action of nitric 

 acid upon it, and its conversion into Picric acid, which is deposited in 

 yellow crystals. Picric acid is also known under the names of Carbazotic 

 acid and Nitrophenic acid, and was introduced for dyeing purposes about 

 six years ago by Messrs. Guinon, Marnas, and Bonny, of Lyons. The colour- 

 ing property is very considerable, one part of the acid in 300,000 parts 

 of water communicates a yellow tinge to the liquid. All animal fabrics 

 are dyed with facility of a brilliant yellow and fast colour, one part 

 of picric acid in water with a little sulphuric acid gives 1,000 times 

 its weight of silk a moderate yellow colour. Acted upon by the pro - 

 toxide of iron, a red dye (picramic acid) is the result, whilst with oxide 

 of copper it gives a yellow green dye. The blue dye, Azuline, is pre- 

 pared by the action of Aniline on Peonine. On account of the property 

 which picric acid has, of forming sparingly soluble salts with potash, it 

 is used as a test with that alkali. Its well marked colour and bitter 

 taste has caused it to be employed for mixing with some poisonous sub- 

 stances for the purpose of preventing accidents. Picric acid has medici- 

 nal properties, having anti-periodic powers similar to quinine. One 

 great impediment to its administration exists in the fact that a yellow 

 colour of the skin is produced in those to whom it is administered. 



Mr. Bethell has proposed with great advantage the employment of 

 oil of tar as a method of preserving wood and preventing decay in 

 timber ; this power is in a great measure due to the carbolic acid of 

 the oil. The protection is due to the prevention of absorption of mois- 

 ture, to the coagulation of the albumen, to the general prevention of 

 decomposition, and is at the same time so noxious to animal and vege- 

 table life, that the attacks of insects are repelled, and the growth and 

 propagation of fungi prevented. The mode of application consists in 

 placing the timber in strong closed cylinders under pressure, similar to 

 a steam boiler ; a vacuum is produced by an air-pump, and the hydro- 

 carbon forced into the wood by a pressure of 1501bs. on the square inch. 

 As much as 181b. have been forced into a cubic foot. When a quantity 

 equal to 101b. to each cubic foot has been forced in, the process is com- 

 plete. Railway sleepers prepared in this manner have been in use for 

 twenty years, and at the end of that time found comparatively sound. 

 It is said that by this process the common and softer woods, such as 

 Scotch fir, are rendered as durable and firm as the best oak. The gene- 

 ral use of this method of preserving wood on a large scale resolves itself 

 into a question of cost. 



