53 DISTILLATION, DESTRUCTIVE 



should bo placed on various parts of tho lid of tlio pot, so as to keep it, close, 

 and render tho leakage as little as possible. For tho destructive distillation of small 

 quantities of substances, I havo been accustomed for a long time to employ a small 

 still mado from a gluo pot, and having a copper head made to fit it. Tho luting for 

 all temperatures not reaching above 700 may bo a mixture of ths linsood and ^[th 

 almond meal, mado into a mass of the consistency of putty. For thu apparatus em- 

 ployed in the destructive distillation of wood, coal, bones, &c., on the largo scale, tho 

 various articles in this work on the products obtained from those substances must be 

 consulted. 



2. Destructive distillation of vegetable matters. Tho principal vegetable matters 

 which are distilled on tho large scale aro wood and coal. Wo shall consider these 

 separately. 



Destructive distillation of wood. The products obtained in the ordinary process of 

 working are acetic acid, wood spirit or methylic alcohol, acetone, pyroxanthiue, xylite, 

 lignine, paraffine, creosote or phenic acid, oxyphenic acid, pittacal, several homologucs 

 of benzole, with ammonia, and methylamino. There are also several other bodies 

 of which the true nature is imperfectly known. The greater part of tho above sub- 

 stances are fully described in separate articles in this work. See ACETIC ACID; 

 PARAFFINE, &c. 



Peat appears to yield products almost identical with those from wood. 



Destructive distillation of coal. The number of substances yielded by tho distillation 

 of coal is astonishing. It is very remarkable that tho fluid hydrocarbons produced at 

 a low temperature are very different to those distilling when a more powerful heat is 

 employed. The principal fluid hydrocarbons produced by the distillation and subse- 

 quent rectification of ordinary gas-tar are benzole and its homologues. See HYDRO- 

 CARBONS. But if the distillate is procured at as low a temperature as possible, or 

 Boghead coal bo employed, the naphtha is lighter, and the hydrocarbons which make 

 its chief bulk belong to other series. See NAPHTHA. 



3. Destructive distillation of animal matters. Bones aro the principal animal sub- 

 stances distilled on the large scale. The naphthas which come over are excessively 

 fetid, and are very troublesome to render clean enough for use. The products con- 

 tained in bone-oil will be described in the article NAPHTHA. Horn and wool have 

 been examined with reference to the basic products yielded on distilling them with 

 potash. Horn under these circumstances yields ammonia and amylamine. Wool I 

 find to afford ammonia, pyrrol, butylamine, and amylamine. My experiments on 

 feathers, made some years ago, although not carried so far as* those on wool, appear to 

 indicate a very similar decomposition. 



The products yielded by animal matters, when distilled per se, are very different 

 to those obtained when a powerful alkali is added previous to tho application of 

 heat. If feathers or wool be distilled alone, a disgustingly-foetid gas is evolved, 

 containing a large quantity of sulphur. Part of the sulphur is in the state of sulphide 

 of carbon. But if an alkali be added previous to the distillation, the sulphur is re- 

 tained, and the odour evolved, although powerful, is by no means offensive. During 

 the whole period of the distillation of ordinary organic matters containing nitrogen, 

 pyrrol is given off, and may be recognised by the reaction afforded with a slip of deal 

 wood dipped in hydrochloric acid. An interesting experiment, showing the formation 

 of pyrrol from animal matters, may at any time bo made with a lock of hair, or the 

 feather of a quill. For this purpose the nitrogenous animal matter is to be placed at 

 the bottom of a test tube, and a little filtering paper is to be placed half way up tho 

 tube, to prevent the water formed during the experiment from returning and frac- 

 turing the glass. The end of tho tube is now to bo cautiously heated with a spirit 

 lamp, and, as soon as a dark yellowish smoke is copiously evolved, a slip of deal pre- 

 viously moistened with concentrated hydrochloric acid is to be exposed to the vapour. 

 In a few seconds the wood will acquire a deep crimson colour. Tho fact of tho pre- 

 sence of sulphur in wool, hair, or other albuminous compounds of that descripi ion, 

 may bo made very evident to an audience by the following experiment. Dissolve the 

 animal matter in very concentrated solution of potash in a silver or platinum basin, 

 with tho aid of heat. Evaporate to dryness, and raise tho heat at the end to fuse the 

 potash and destroy most of tho organic matters. When cold, dissolve in water, and 

 filter into a flask half full of distilled water. To tho clear liquid add a little of Dr. 

 Playfair's nitroprussido of sodium ; a magnificent purple tint will bo immediately pro- 

 duced, indicative of the presence of sulphur. A very small quantity of hair or flannel 

 will suffice to yield tho reaction. 



The above remarks on destructive distillation apply principally to highly complex 

 bodies, the molecular constitution of which is cither doubtful, as in tho case of albu- 

 minous substances, or totally unknown, as with coals and shales. Tho destructive 

 distillation of organic substances of comparatively simple constitution, such as acids 



