542 



NATURE 



[April 29, 1922 



information was begun by Mr. W. Macnab under the 

 Ministry of Munitions, and thanks are due to the 

 Department of Scientific and Industrial Research for 

 arranging for his retention to complete it. 



Denitration. — The first volume deals with the re- 

 covery of the nitric and sulphuric acids from the waste 

 acid produced in the nitration of toluene and glycerine. 

 Not only is the proportion of waste acid a large one — 

 650 tons for 100 tons of trinitrotoluene produced — 

 but the eflficient recovery of the sulphuric acid in a 

 condition suitable for concentration, and of the nitrogen 

 oxy-acids as nitric acid, constitutes one of the principal 

 economic factors of the manufacture. 



The chemical reactions involved in denitration have 

 been the subject of discussion both earlier and as a 

 result of experience in war factories, and the position 

 is summed up in the introduction to this volume. It 

 may briefly be said that by considering the behaviour of 

 nitrosylsulphuric acid when it acts on nitric acid, and 

 when it breaks down on dilution with water, a fairly 

 coherent explanation is afforded of what goes on during 

 the progress of waste acids down a denitrating tower 

 as they meet an ascending current of steam. 



The treatment of the subject of the absorption of 

 the nitrous fumes coming from the towers to form 

 55 per cent, nitric acid is of importance at the present 

 time, when this problem confronts any manufacturer 

 proposing to make nitric acid by the catalytic oxida- 

 tion of ammonia. The experience recorded is that a 

 90 per cent, conversion of nitrogen peroxide to nitric 

 acid can be secured with a ratio of free tower space to 

 rate of passage of nitrogen peroxide, which is less than 

 a tenth of that in large towers erected for the same 

 purpose in connection with the oxidation of ammonia. 

 The relative effectiveness of the small towers with the 

 most advantageous conditions of concentration and 

 velocity of gases and free space, temperature, and 

 concentration of nitric acid, is clearly indicated, and 

 forms a basis for modification of the present practice 

 of installing immense absorption towers which are 

 obviously inefficient and very costly. 



Full detailed drawings are given of the plant for 

 the processes of denitration, absorption, and storage 

 of acids, and its applicabiUty to the manufacture of 

 organic nitro-bodies should make the report of interest 

 and importance to a wider field than that of the 

 explosive manufacturer alone. 



Trinitrotoluene Manufacture. — No. 2 of this series 

 gives the history of processes for making trinitro- 

 toluene and for its purification, and describes plant and 

 manufacturing methods. An account is given of the 

 experimental work at the Research Department, 

 Woolwich, which established the conditions necessary 

 for nitration, the advantage of the extraction of waste 

 NO. 2739, VOL. 109] 



acids (" detoluation ") by mononitrotoluene, itself to 

 be nitrated later, and the benefits of a cyclic system of 

 nitration in stages in order to conserve acids. These 

 features were embodied in the processes followed in 

 the large factories erected for making trinitrotoluene, 

 an important variation, however, being the elaboration 

 at Oldbury of the counter-current method into a con- 

 tinuous process, which had a high capacity combined 

 with low labour and capital cost. 



In the process as carried out at the largest factory. 

 Queen's Ferry, mononitrotoluene, made separately 

 either by nitrating gas-works toluene or the toluene 

 contained in Borneo petroleum, was used to detoluate 

 waste acids which had themselves been detoluated 

 by once-used mononitrotoluene, brought up to nearly 

 dinitrotoluene in the last-mentioned operation, and 

 this dinitrotoluene was then nitrated to trinitrotoluene. 



The next process, that of freeing the crude tri- 

 nitrotoluene from acids, underwent some elaboration, 

 for in addition to agitation of the molten trinitro- 

 toluene by hot water it was found efficacious to chill 

 it by pelleting it in cold water, and to use weakly basic 

 hydrolysable salts for the hot washing ;, a continuous 

 system of hot washing was also developed. 



But although it became possible latterly to push 

 the process of nitration until nearly all the dinitro- 

 toluene had been converted into trinitrotoluene, there 

 remained about 4 per cent, of its unsymmetrical 

 isomerides resulting from the nitration of the meta- 

 nitrotoluene. While the crude trinitrotoluene, after 

 having been washed and dried, could be used in large 

 quantities for making the bulk of the amatol for filling 

 shell, there were certain purposes for which a purer pro- 

 duct was demanded, when, for example, the ammonium 

 nitrate was not fiee from pyridine and thiocyanate, or 

 when it was necessary to avoid the low melting-point 

 eutectics formed by the isomerides. Purified trinitro- 

 toluene was prepared at first by crystallisation from, 

 or by washing with, organic solvents, and large factories 

 were erected for these purposes. Later, a process was 

 from the French, safer from the point of view 



of fire-risk, and characterised by treating the crude 

 trinitrotoluene with sodium sulphite solution which 

 under suitable conditions selectively dissolves out the 

 other isomerides, leaving the pure symmetrical trinitro- 

 toluene and any dinitrotoluene that has escaped 

 further nitration. As this process was one which 

 could readily be embodied in- the scheme of manu- 

 facture, it was carried out in the trinitrotoluene factory. 

 The plant at Queen's Ferry, which in every detail 

 is stamped with the genius of Mr. K. B. Quinan, is 

 described in this volume in all relevant particulars 

 as to the main features of the manufacture. The 

 reproductions of the working drawings, the diagrams 



