Oct. 26, 1882] 



NATURE 



621 



tific knowledge, could have been found to undertake the 

 work. Already in 1867 Dr. Lunge had published a 

 tieatise in German on the subject ; this has now been 

 elaborated into the present excellent work, which de- 

 scribes the processes of manufacture as carried on in the 

 largest and best arranged tar and ammonia works in 

 England and the Continent. In the preparation of the 

 newer work the author has received much assistance from 

 Mr. Watson Smith, who has extensive knowledge of these 

 processes as carried out in Lancashire. 



Chapter I. is mainly concerned with the origin of coal- 

 tar ; with historical notes on its applications, and with 

 the general characters of the tars obtained from various 

 sources. Much in this chapter, as indeed in other parts 

 of the work, is of direct interest to the gas-engineer. An 

 iron smelter has been defined as one who makes slag, 

 and the economical production of cast-iron is very much 

 a question of the economical production of the proper 

 sort of slag. So important indeed are, nowadays, the 

 " residual " products in the manufacture of coal-gas that 

 a gas-engineer may with even greater truth be described 

 as a maker of coal tar and ammonia-water, and we fully 

 agree with Dr. Lunge that with the electric light looming 

 in the near future, gas managers will have to consider the 

 market prices of these "residuals," as influencing the 

 mode of their manufacture, more carefully than they have 

 hitherto done. They must in fact recognise that they 

 are just as much makers of tar and ammonia as of coal- 

 gas, and whether the one or the other is to be worked for 

 must be governed by calculations depending upon the 

 relative prices of gas and tar. 



Chapter II. deals mainly with the properties of coal-tar 

 and its constituents. A very complete list of these is 

 given, and special attention is paid to their physical cha- 

 racters whenever these have been ascertained. Benzene, 

 of course, is very fully described, even to an account of 

 the rival theories of Kekuld, Claus, and Ladenburg as to 

 its constitution. We entirely endorse Dr. Lunge's recog- 

 nition of the enormous value of Kekule"'s famous hypo- 

 thesis in the development of the history of the aromatic 

 derivatives ; nevertheless the average tar distiller will, we 

 are afraid, be lost in wonder and amazement at the idea 

 of such fruitful consequences flowing from pictures of 

 hexagons and prisms. In other words the description on 

 p. 40 of the chemical constitution of the parent member 

 of the aromatic group is far too bald to be of the slightest 

 use to persons ignorant of the modern methods of repre- 

 senting constitution, and conveys no new information to 

 those who know anything of such matters. 



Chapter III. treats of the applications of coal-tar with- 

 out distillation, such as its use for gas making, heating, 

 and for the preservation of building materials and its use 

 as an antiseptic, and in the manufacture of paints, var- 

 nishes, &c. Chapter IV. deals with the methods of dis- 

 tilling coal-tar, such as its distillation by steam and by 

 fire. This and the next chapter (Chapter V.), on pitch, 

 are extremely well illustrated by cuts and plates showing 

 the best methods of constructing stills and condensing 

 apparatus, mode of treating the gases and the different 

 fractions, and a series of most valuable figures and tables 

 are given of the results obtained in various works in 

 England and on the Continent from different tars. 

 Chapters VI. and VII. treat of anthracene and creosote 



oil, and considerable attention is given to the important 

 question of the quantitative determination of anthracene 

 and of the so-called coal-tar acids. Chapter VIII. is 

 concerned with phenol or carbolic acid and naphthalene, 

 and contains many valuable details as to the manufacture 

 of carbolic acid hitherto unpublished : we would especially 

 instance the careful description of the manufacture of 

 pure phenol, as carried on in Lancashire which is fur- 

 nished by Mr. Watson Smith. Chapters IX. and X. 

 treat of what is technically known as "light oil"or "crude 

 naphtha," and of its rectification by steam. The last 

 chapter (Chap. XI.) is entirely devoted to the subject of 

 gas-liquor, or the ammoniacal liquor obtained at the gas 

 works by condensation in the hydraulic main and by 

 washing the gas in the scrubbers. Ammonia is in fact 

 one of the most important products of the destructive 

 distillation of coal ; indeed the supply falls very far short of 

 the demand made by the employment of ammoniacal salts 

 in artificial manures and in the manufacture of soda ash by 

 the modern method. The price of sulphate of ammonia 

 has been pratically doubled within the last twenty years. 

 Whether ammonia will ever be produced commercially 

 from the nitrogen of the air is a vexed question, but there 

 is no doubt that if the coking of coals could only be 

 carried out in a rational manner we might count upon an 

 important addition to our stock of ammonia and of tar. 

 It is indeed to this source that we must more immediately 

 look for the increased supply so urgently needed. 



Dr. Lunge has already enriched our literature by a 

 most valuable treatise on another of our most important 

 chemical industries, viz. the manufacture of alkali, and 

 he has still further added to our debt by the publica- 

 tion of the present excellent manual. The work is ex- 

 tremely well got up, and deserves to be on the table of 

 every gas manager and tar distiller in the kingdom. 



T. E. Thorpe 



OUR BOOK SHELF 

 Tables for the Qualitative Analysis of " Simple Salts" 

 and "" Easy Mixtures!' By Joseph Barnes. (Man- 

 chester : James Gait and Co. ; London : Simpkin, 

 Marshall, and Co., 1S82.) 

 These tables are evidently compiled by one who has had 

 considerable experience in teaching qualitative analysis ; 

 the directions are always clear and to the point ; the 

 student is not confused by too many alternative methods, 

 neither is the art of anal) sis made altogether a matter to 

 be learnt by rote. The short and simple solubilities table 

 on p. 37 is especially to be commended. If we must have 

 yet another set of tables for elementary qualitative analysis 

 let us have these by Mr. Barnes; but have we not sufficient 

 already ? 



LETTERS TO THE EDITOR 

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The Comet 



and 



At 4.30 this morning this comet was a most conspicuous ana 

 rely object in the clear sky, in the south-east. With the 



