402 NAPHTHALINE DYES 



naphthaline are not yet discovered, it is a -well-known fact that naphthaline shows 

 a great affinity for light hydrocarbons. In gas generated at a low temperature, many 

 of the volatile substances are lost in an undistilled condition, with the tar in the 

 hydraulic main and connecting pipes, in their liquid form, and combine with, or rather, 

 take up, the naphthaline. Under an increased heat the greater part of these oils 

 would form fixed gas, and consequently increase the volume of the gas manufactured. 

 Though it is a great advantage to make use of as great a quantity of these lighter 

 oils as possible in distilling the same to gas, we all know that all the lighter oils 

 cannot be used up entirely in the distillation of cold, and thus it seems the duty of an 

 enlightened gas-engineer not to waste the same, but to make a judicious use of it in 

 keeping the gas as long as possible in contact with the gaseous vapours, and thus 

 preventing the crystallisation of the naphthaline which is contained in the gas. The 

 lighter oils, as long as they are united, will, whenever they settle down in a condensed 

 state, carry away a great deal of naphthaline in a liquid form, and the naphthaline 

 will, in a pipe placed in proper descent, be carried on to the drips. The lighter-oil 

 vapours will separate from the gas at low temperature ; in condensing, therefore, it is 

 thought by many best that the take-off pipes from the hydraulic main should be nearly 

 on a level with the same, and should be of sufficient length. Clegg gives as a rule, 

 that for every inch of diameter, the take-off pipe should have a length of ten feet, the 

 working pressure being two inches ; for instance, the take-off pipe being ten inches in 

 diameter, the proper length would be one hundred_feet. By increased working pres- 

 sure they will of course require increased length in the ratio of their square roots ; 

 but even at this rate a great deal of the lighter oils will be lost in condensation. 



It had been found by experience that those oils, if collected in a little tank and 

 re-vapourised, will greatly diminish the tendency of the naphthaline to crystallise, and 

 at the same time improve the quality of the gas. The form of such an apparatus 

 should be a small iron tank, closed at the top, and placed below the level of inlet pipe 

 of the condenser, to which all drip water, and with it the lighter oils, must be con- 

 ducted ; the lighter oils will, from the nature of their specific gravity, float on the top 

 of the tank. By passing a coil of steam-pipes through the tank the lighter oils will 

 be vapourised, and the naphthaline will settle at the bottom, and from there can, 

 from time to time, be let off. If there be an insufficient amount of these lighter oils, 

 some benzine, benzole, or naphtha can be added with advantage, particularly if coal 

 be used containing only a small proportion of these lighter oils. Hydrocarbon-vapours 

 will surely liquefy naphthaline in any pipe or vessel. 



A further tendency of naphthaline to crystallise will be created if gas containing 

 naphthaline is passed in from a hot to a cold place ; say, for instance, if the gas be 

 stored in the holder, and the same, without a building, is exposed to the heat of a high 

 temperature ; when let into pipes in the ground, which are located in a lower tem- 

 perature, naphthaline will surely crystallise, and in course of time Tvill stop up the 

 pipes more or less ; or if the street mains are, in certain locations, laid too near the 

 surface of the ground, and afterwards the gas be passed into pipes located in lower 

 ground, by which a variation of temperature is created, naphthaline will have a 

 tendency to crystallise. 



Kecently the derivatives of naphthaline, which are almost innumerable, have been 

 receiving much attention ; and many colouring-matters are produced by its reactions. 

 These have not, however, as yet found a place, to any considerable extent, in com- 

 merce. 



Naphthylin, Diamine Violet, Naphthalin Yellow (known also as Manchester Yellow 

 and Jauno d'Or) are described in Crookes's ' Practical Handbook of Colours,' and 

 "Watts's ' Dictionary of Chemistry.' See also NAPHTHALINE DYES. 



VTAPHTHAXiXDIirE. See NAPHTHYLAMINE. 



NAPHTHAl-IirE. _ C 20 H 8 (C 10 H 8 ). A solid, crystalline hydrocarbon contained 

 in coal-tar. It is especially interesting in consequence of its being the substance 

 so long and persevenngly studied by Laurent. Its combinations and derivatives 

 are immensely numerous, and, in a theoretical point of view, of the greatest im- 

 portance, the well-established theory of substitutions being, to a great extent, 

 founded upon the results obtained by treating naphthaline with nitric acid and the 

 halogens. 



NAPHTHAIiITTE DYES. Within the last few years a number of colouring- 

 matters, some of which are employed commercially, have been obtained from naph- 

 thylamino, itself a derivative from naphthaline. In preparing naphthaline red, or as 

 it is often called, Magdala red, the naphthylamine is first converted into azodinaphthyl- 

 diamine, by the action of nitrous acid ; and this, wheu treated with naphthylamine, 

 yields a peculiar base, which forms naphthaline red. Naphthaline blue and naphtha- 

 line violet are obtained by acting on the red base with iodide of methyl, or iodide of 

 ethyl, or by treating it with pernitrate of mercury, chloride of copper, chlorate of 





