THE COLLIERY GUARDIAN 1135 December 3, 1915. ____________________________ Coal Tar. The composition of tars varies enormously with the apparatus employed, the coal used, the method of work- ing, etc. Lunge quotes the two following sets of values for gas works tar, which may be taken as typical. These tars were made from the same coal in the same works; but in the one case the coal was coked in a horizontal retort, and in the other in a vertical retort. Analysis of G-as Works Tar. Specific gravity, about.......... Free carbon ................. Distillation yields: - Water..................... Light oil................... Middle oil ................. Heavy oil ................. Anthracene oil.............. Pitch ..................... Vertical. 1*1 Per cent. 2—4 Horizontal. 1’2 Per cent. ... 20*0 2*2 3'5 5'9 3T 12*3 7’7 12’0 ... 10*2 160 ... 11’6 49*7 ... 62*0 Coke oven tar usually contains less free carbon than ordinary tar, and is therefore more mobile. Its specific gravity is from 1’14 to 1-19, and when distilled it yields on an average the following products :— Analysis of Coke Oven Tar. Per cent. Water ................... 2*7 Light oil ................. 1’4 Middle oil ............... 3 5 Heavy oil................. 9’9 Anthracene oil ............ 24’8 Pitch.................... 56*4 Tar from gas producers differs from the above in that it contains considerable quantities of water. A sample of gas producer tar gave the following distillates :— Analysis of Gas Producer Tar. Per cent. Below 230 degs. Cent........... 230 degs. Cent .—300 degs. Cent.... From 300 degs. until oil solidified Oils solidifying on cooling .... Coke .......................... Water and loss................ 5’4 by volume. 10T 14*5 10'4 30*5 by weight. 32*6 A tar commonly found in gas works is water gas tar. This is not actually a product of coal, but is produced by the cracking of the oil used for carburetting the water gas. It is thinner than ordinary tar, is usually brown in colour, and contains much water. The amounts of free carbon and of phenols in this tar are minute, and the higher boiling oils produced from it contain only small quantities of naphthalene and anthracene. Dehydrated tar finds wide application in the pre- paration of roofing felt, and for preserving timber, stone, iron, etc. Tar has, weight for weight, a slightly higher heating value than coke, and is now being used as a fuel. Formerly it was simply poured on to solid fuel, but under these conditions combustion was by no means complete; now the tar is usually injected in the form of a fine spray by means of steam or air, and so comes in intimate contact with the air, this resulting in com- plete combustion. Tar is sometimes simply mixed with coke for heating retorts in a gas plant, or used in con- junction with coke oven gas for heating coke ovens. It is also converted into a gas by being passed through red- hot tubes. There are so many valuable products which may be obtained from tar that its use as a fuel is, from the standpoint of conservation, to be condemned; but it must be admitted that in very many cases the tar has to be used in this way. Large gas and coke oven plants can profitably have a tar distilling plant in addition; but the distillation of tar in small works is not remunerative. In the latter case, the tar may be shipped to central distilling plants, but even this procedure is not commer- cially possible where the gas or coke oven plant is isolated, and consequently the cost of transportation high. In such cases the use of tar for fuel is the only possible one. Coal tar is distilled in wrought iron stills. These stills are usually upright cylinders of 10 to 20 tons capacity, sometimes heated by steam, but more often by a direct fire. As water in tar sometimes causes bumping in the stills, it is removed as completely as possible before- hand. With thinner tars the water settles out on the surface at ordinary temperatures sufficiently well to be run off, but thicker tars require to be moderately heated to cause a satisfactory separation. The still-head is connected with a condensing worm, from which the various products of distillation are conducted into different receivers. At the end of the distillation process the fire is drawn out, and the temperature allowed to fall to a point at which the pitch left behind in the still— though remaining liquid—will not ignite when it comes in contact with the air. This pitch is then run out into barrels, or other suitable receivers. Sometimes, in the last stages of the distillation, superheated steam or a vacuum is utilised, since either of these causes the high- boiling-point products to pass over at a lower tempera- ture than would otherwise have to be employed. Recently, tar has been successfully treated in continuous distillation apparatus. As is shown below, the various first products of coal tar give, on refinement, numerous compounds of supreme importance in technical chemistry. The amounts of these compounds obtained from tar vary considerably with the nature of the tar itself; and the following figures merely give an approximate idea of the quantities which may be expected from an average coal tar :— Derivatives of coal tar— Per cent. Benzene and homologues.......... 2*5 Phenol and homologues .......... 2*0 Pyridine and other bases.......... 0*25 Naphthalene ..................... 6*0 Heavy oil........................ 22*0 Crude anthracene (30 per cent, pure) 1’5 Pitch............................ 60’0... Water and loss................... 6’0 The light oil, which is 3 to 6 per cent, of the original tar, contains :— Per cent. Phenols..................... 5’0— 15’0 Pyridines................... 1’0— 3’0 {Sulphur compounds ......... 0T Nitriles ................... 0’2— 0’3 Neutral substances.......... 1’0— 1’5 Hydrocarbons................ 80*0—100’0 The hydrocarbons are almost completely aromatic, four-fifths being benzene and its homologues, and one- fifth naphthalene. The middle oil, which constitutes 8 to 12 per cent, of the tar, contains :— Per cent. Phenol .................. 10 Cresols .................. 20 Naphthalene ............. 30 Residue—heavy oil ........ 40 In addition, the oil contains considerable quantities of pyridine and other bases. The heavy oil, 10 to 12 per cent, of the tar, is a semi- liquid product, containing :— Per cent. Naphthalene ............. 30 Cresols and homologues..... 10 Pyridine bases ..... . .......... 6 Unknown hydrocarbons..... 40 Anthracene oil, which is 11 to 16 per cent, of the tar, contains about 3 per cent, pure anthracene, 6 per cent, phenols, and numerous other liquid and solid compounds. Pitch, amounting to as high as 60 per cent, of the weight of tar, contains varying quantities of free carbon; thus coke oven pitch and vertical retort pitch may con- tain as low as 2 per cent, free carbon; while in horizontal retort pitch there may be as much as 40 per cent. Commercial Products of Coal Tar. 90 per cent. Benzol.—Uses : As a solvent for the manufacture of colours, for extracting fat from bones and seeds, and for making iron varnishes; also, as a detergent; as a fuel for internal combustion engines; and for carburetting gas. Derivatives : By distillation, ‘pure benzene, toluene, xylene, etc., are obtained. Benzene is widely used in the preparation of numerous technical organic products. From it nitrobenzene, aniline, etc., are readily obtained, and therefore it is the parent substance of the numerous aniline dyes; of many artificial perfumes; and of photographic developers, etc. Toluene and xylene are used in the preparation of certain dyes. The former gives on nitration trinitro- toluene, a substance used in the manufacture of explosives. 50 per cent. Benzol.—Use : As a substitute for the 90 per cent, benzol in the manufacture of certain dyes. Solvent Naphtha.—Uses : As a solvent for rubber in the preparation of waterproof fabrics; as a detergent; and as a solvent in the purification of anthracene. Crystalline Carbolic Acid. — Use : As an antiseptic. Derivatives: By nitration, carbolic acid gives picric acid, which is used in the manufacture of many impor- tant explosives, and of some dyes. It is the source of many substances used in the colour industry (e.g.9 salicyclic acid), and of certain photographic developers (e.g., metol). Liquid Carbolic Acid.—Uses : As a liquid antiseptic, and as the active principle of disinfectant soaps, powders, etc. Naphthalene.—Uses : For carburetting gas; for disin- fecting purposes; for driving explosive motors; for pre- serving raw hides; and sometimes also for fuel. Crude naphthalene is usually employed for the above purposes. Derivatives : Pure naphthalene is the starting point in the manufacture of a large number of important arti- ficial colours (phthalein colours, azo-colours, indigo, etc.) Heavy Oil (also called Creosote Oil).—Uses : as an illuminant where smoke is no objection; as an anti- septic; as a timber preservative; as a lubricant; as a binder, when mixed with pitch, in the manufacture of patent fuels; as a fuel; and as a solvent. 50 per cent. Anthracene. — Uses : Not important. Derivatives : Anthracene is the raw material from which alizarine and other important colouring matters are manufactured. Anthracene Oil.—Uses : For lubricating purposes; for timber preservation; for making soft from hard pitch; for removing naphthalene from coal gas. Pitch.—Uses: For road making; for preparing arti- cial asphalte by admixture with heavy oil; for manu- facturing varnishes by admixture with middle oil; for making patent fuels, after softening by admixture with heavy or anthracene oil; for insulating cables, etc.; for roofing; and for making coke for electric carbons. ___________________________ Charter-Party Dispute. — In the Commercial Court on Thursday, Mr. Justice Rowlatt gave judgment for plaintiffs (for amount claimed) in an action by Messrs. S. Wright and Company against Messrs. Walter Runciman and Company and Mr. Tomasso Astorito, for damages for breach of a charter-party, dated April 12, 1915, and, alternatively, for damages for breach of warranty of authority in connection with the said charter-party. Plaintiffs’ claim said that by a charter-party dated April 12, 1915, between the plaintiffs, as charterers, and signed by Messrs. Runciman for and by the authority of the owner, Tomasso Astorita, it was agreed that a steamer to be named should proceed to Newport and load from the charterers a full and complete cargo of coal not exceeding 3,630 tons nor less than 2,970 tons, and deliver the same at Palermo, Cagliaria, or Messina (orders before sail- ing), on being paid freight at 21s. per ton. By a letter dated April 15, 1915, Messrs. Runciman advised the plaintiffs that the said charter-party would not be fulfilled. Plaintiffs were thereupon compelled to effect a substituted charter with the owners of the steamer “ Beatus ” at a rate of 36s. per ton. Plaintiffs suffered by reason of this difference in freight, and claimed .£2,929 10s. 9d. from Messrs. Runciman as agents for a foreign principal as damages for breach of the charter- party, or, alternatively, the same amount as damages for breach of warranty of authority if in fact they had no authority to bind the said owner. Plaintiffs also claimed the same amount of damages against Tomasso Astorita, the ship- owner. . BOOK NOTICES. Analyst and Client. By C. H. Ridsdale, F.I.C., F.C.S., and N. D. Ridsdale, F.C.S. 198 pp. 8J in. x 3| in. Middlesbrough : Ridsdale and Company; 1915. Price, cloth 6s., leather 8s;, edition de luxe 10s. 6d. Thia handy volume contains “ a few notes on chemical and physical testing and other technical matters, with 17 original tables and a special section on electrical conductor rail tests, for the constant use of railway and works managers, engineers, secretaries, buyers, and other business men connected with metallurgical indus- tries.” The authors have particularly in view the rela- tion between analyst and client, and the best way to turn chemical and allied information to account in industrial life. The book is intended to help analyst and client to understand each other better, and especially to indicate the various ways in which an experienced chemist can assist in industrial developments. It is true that many public analysts, owing to deficient works experience, fail to extend their sphere of usefulness beyond the mere routine work of their laboratories. The matter is divided into three sections. After an intro- ductory note on analysis, section 1 deals with sampling as applied mainly to metallurgical materials. There are useful hints as to necessary precautions to be taken in special cases. The work of the analyst is then explained, and a useful table gives the necessary data for the inter- pretation of analyses. The international atomic weights are here included, as well as the old round numbers familiar to our school days. A useful table of abbrevia- tions, and, finally, this section concludes with a table showing a few of the principal types of materials, with the chemical constituents usually required to be deter- mined. Amongst these, naturally coal and coke take a prominent place. Section 2 deals with matters other than sampling and analysis, and appeals to the experi- enced technical specialist only. In this section is given the kind of information a client should be in a position to supply for the guidance of the specialist. There are also hints on laboratory tests as a guide to behaviour in practice, on consultations, research and investigations, and matters specially applicable to the iron and steel industry. A table gives examples of the kind of infor- mation required in various sections of industry, and a number of ruled pages are supplied for recording analyses of particular interest, with examples of entry of a few typical cases. Section 3 gives various conversion factors, tables and data for the testing of steel conductor rails, for the use of railway engineers and works managers, contractors, or inspectors. The growth of the use of electrical transmission has given increased import- ance to the testing of conductor rails, and the authors claim that the tables supplied were the first of this character to be published. These were formerly issued as separate sheets, and are now incorporated in this volume. They have proved their value, and should be greatly appreciated in their present form. This booklet is well printed and elegantly produced in a form convenient for the pocket. It is likely to be widely used, especially in the metallurgical world, to whose attention we commend it without hesitation. An Introduction to Applied Mechanics. By Ewart 8. Andrews, B.Sc. Cambridge Technical Series. 316 pp. and 184 illus. Cambridge : University Press. Price, 4s. 6d. net. As the author rightly says in the preface to this book, teachers of engineering and architecture have found applied mechanics a difficult science to teach, while students coming freshly to its study admit it to be one of their most troublesome subjects. Many of the exist- ing treatises contain too much applied mathematics, and others too much practical application, without sufficient explanation of the elementary principles. The author has attempted to steer between these two extremes, and to present the elementary principles of mechanics in accurate and clear terms, showing at the same time the application of these principles to simple practical pro- blems. He bases his general treatment upon graphical conceptions rather than purely mathematical analyses, as the student more easily reasons from diagrams than symbols. Commencing with a discussion of forces and their diagrammatic representation, the author passes through successive chapters on moments, work, machines, efficiency, velocity, energy, Newton’s laws, and stress and strain, to the consideration of riveted joints, then cylinders, forces in framed structures, beams and girders, centre of gravity, friction, curved motion, mechanisms, and belt, chain, and toothed gear- ing. The volume concludes with an appendix of “ rour- place ” mathematical tables, including logs, anti-logs, and trigonometrical ratios. The book as a whole is clearly written, easy to follow, and well set out, and should be a great help to many students who find diffi- culty in grasping the elements of this important science. ____________________________ Important Railway Rates Case.—The Railway and Canal Commission on Thursday reserved judgment in the applica- tion of the Associated Portland Cement Manufacturers Limited and others to compel the Great Northern Railway to justify and increase made in railway rates under the Railway and Canal Traffic Act, 1913. As a result of the railway strike in August 1911, and the intervention of the Government, the railway companies agreed to grant increased wages to their workmen; and in 1913 the com- panies were authorised by Act of Parliament to increase their rates for goods traffic to meet the rise in cost of working the railway due to improvements made since August 1911, in the conditions of employment. The applicants in this case complained that rates by which their traffic was affected had been increased. The respondents admitted the increase, and said that it had been made in accordance with the Act, to recoup them for the rise in the cost of working. The question at issue, therefore, was what meaning was to be given to the phrase “ rise in the cost of working.”