888 NAPHTHA 



is to be changed, and so on at every 10. "When the whole fluid is distilled away, a 

 smaller retort is to be taken, capable of well holding each 10-fraction, without fear 

 of anything boiling over. Suppose the first fraction of the first distillation came over 

 between 100 and 110, it is to be placed in the retort, and the distillation carried on 

 as before. But it will, in almost every instance, be found that the boiling-point 

 will have been reduced 30 or 40 by the removal of the fluids of higher boiling- 

 point. Under any circumstances, however, the distillate is to be received in bottles, 

 and labelled with the boiling-point and the number of the rectification. When all 

 the first 10-degree fraction has distilled away into the second series of bottles, the 

 next is to be operated on, and so on. By this means only two series of bottles are 

 ever being used at once, viz., the series being distilled, and the series being distilled 

 into. Many fluids may be obtained of steady boiling-point by 15 or 16 rectifications, 

 involving, in the case of 10 fractions in each series, at least 150 distillations. But 

 most complex organic fluids, such as naphthas, have a much wider range of boiling- 

 point than 100. Boghead-naphtha, for example, commences at about 289 Fahr., 

 and rises above 500. But in the second distillation, the first fraction, instead of dis- 

 tilling at 289, came over at 250, the depression of boiling-point being nearly 40. 

 By proceeding in this manner six times, a fraction was obtained boiling at 210. 

 When a 10-fraction no longer splits up during distillation, that is to say, when it 

 comes over almost between the same points at which it last distilled, it will be 

 proper to commence the separation of the various substances present in each frac- 

 tion. Before doing this, it is often advisable to make a few preliminary experi- 

 ments, with the view of ascertaining the nature of the fluids present. The more 

 volatile portions may be tested for benzole by converting them into aniline in the 

 method given in the article BENZOLE. The simplest way of detecting the OH> 

 series (homologous with olefiant gas ; see HOMOLOGOUS) will be by ascertaining 

 whether the naphtha is capable of decolourising weak bromine-water. Supposing 

 the presence of these to have been demonstrated, the complete separation of the 

 hydrocarbons may be effected as follows : Four or five ounces of bromine are to 

 be placed in a large flask, capable of being closed with a well-fitting stopper. About 

 eight volumes of water are then added, and the naphtha of the most volatile fraction 

 is to be poured in by very small portions, the contents of the flask being well shaken 

 after each addition. 



By this mode of proceeding/'.the dark colour of the bromine will gradually fade, 

 and finally disappear. In order to insure a complete reaction, it is better at this 

 stage to add a little more bromine, until the colour is permanent after shaking. A 

 little mercury is now to be poured in, and agitated with the fluids in the flask, to 

 remove all excess of bromine. The oily bromine-compound is now to be separated 

 by means of a tap-funnel, from the mercury and water, and digested with chloride 

 of calcium until every trace of water is removed. The dry brominated oil is now to 

 be distilled, when the radical and benzole series of hydrocarbons will distil away, 

 leaving the brominated oil, which may then be distilled into a vessel by itself. 

 The next step will be to separate the radicals from the benzole series' For this 

 purpose long-necked assay-flasks are necessary. Into one of these vessels, of 3 or 

 4 ounces capacity, 2 drachms of nitric acid should be poured ; 1 drachm of the 

 naphtha is then to be added by very small portions, the flask being kept cool by 

 immersion in cold water. It is essential during the whole time to keep the flask 

 in active motion, in order to bring the hydrocarbon and acid into close contact, and 

 also to cool the contents. If this last precaution be neglected, a violent reaction will 

 occur, and cause the loss of the greater portion of the fluid. When the whole of 

 the drachm of acid has been added, and it is found that the temperature no longer 

 rises on removing the flask from the cold water, the product is to be poured into a 

 narrow and conical glass, and allowed to repose until the hydrocarbon, unacted on, 

 rises to the surface in the form of a transparent brilliant green fluid. The fluid below 

 is then to be removed by means of a pipette, furnished at the upper end with a hollow 

 elastic ball of vulcanised caoutchouc. By this means suction with the lips becomes 

 unnecessary, and the vapours of hyponitric acid are prevented from irritating the 

 lungs. The indifferent hydrocarbon that is, the fluid unacted on by the acid is as 

 yet by no means pure ; it obstinately retains traces of the benzole and OH" series. 

 It is, therefore, to be transferred to a flask furnished with a well-fitting stopper, and 

 treated with nitric acid (specific gravity 1 '5) a considerable number of times. This 

 second treatment may, without any danger of any explosive reaction, be made upon 

 one or two ounces of the partially-purified hydrocarbon. When it is found that the 

 separated nitric acid no longer produces milkiness on being thrown into water, it 

 may be assumed that the benzole and Oil" class of hydrocarbons are entirely re- 

 moved. When the treatment with acid lias been repeated a sufficient number of 

 times, the fluid is to be placed in a clean flask, and well .agitated with a solution 



