3o8 



THE ALUMNI JOURNAL. 



THE MANUFACTURE OF CHLORINE. 



By Dr. LuDWiG Mond, f.r.s. 



{Continued) 



The process has been at work at St. 

 Rollox for over fifty years, and, as far as 

 I know, is there, still in operation, but I 

 am not aware that it has ever been taken 

 up elsewhere. 



Within the last few years, however, 

 several serious attempts have been made 

 to give to this process a wider scope by 

 regenerating nitric acid from the nitro- 

 sulphuric acid and employing it over and 

 over again to convert hydrochloric acid 

 into chlorine. Quite a number of pat- 

 ents have been taken out for this pur- 

 pose, all employing atmospheric air for 

 reconverting the nitrous oxides into 

 nitric acid, and differing mainly in de- 

 tails of apparatus and methods of work, 

 and several of these have been put to 

 practical test on a fairly large scale in 

 this neighborhood, and also in Glasgow, 

 Middlesbrough and elsewhere. As I do 

 not want to keep you here the whole 

 afternoon I have to draw the line some- 

 where as to what I shall include in this 

 brief history of the manufacture of 

 chlorine, and have had to decide to re- 

 strict myself to those methods which 

 have actually attained the rank of manu- 

 facturing processes on a large scale. As 

 none of the processes just referred to 

 have attained that position, you will ex- 

 cuse me for not entering into further de- 

 tails respecting them. 



Mr. Dunlop's process only produced a 

 very small portion of the chlorine manu- 

 factured at that time at St. Rollox, the 

 remainder being made, as before, from 

 native manganese and muriatic acid, 

 leaving behind the very offensive waste 

 liquors I have mentioned before, which 

 increased from year to year, and became 

 more and more difficult to get rid of. 

 The problem of recovering from these 



liquors the manganese in the form of per- 

 oxide, Mr. Dunlop succeeded in solving 

 in 1855. 



He neutralized the free acid and pre- 

 cipitated the iron present by treating 

 these liquors with ground chalk in the 

 cold and settling out, and in later years 

 filter-pressing the precipitate, which left 

 him a solution of chloride of manganese, 

 mixed only with chloride of calcium. 

 This was treated with a fresh quantity of 

 milk of chalk, but this time under pres- 

 sure in closed vessels provided with agi- 

 tators and heated by steam, under which 

 conditions all the manganese was pre- 

 cipitated as carbonate of manganese. 

 This precipitate was filtered off and well 

 drained, and was then passed on iron 

 trays mounted on carriages through long 

 chambers, in which it was exposed to 

 hot air at a temperature of 300° C, the 

 process being practically made continu- 

 ous, one tray at the one end being taken 

 out of these chambers and a fresh tray 

 being put in at the other end. One pas- 

 sage through these chambers sufficed to 

 convert the carbonate of manganese into 

 peroxide, which was used in place of and 

 in the same way as the native mangan- 

 ese. 



The whole of the residual liquors made 

 at the large works at St. Rollox have 

 been treated by this process with signal 

 success for a long number of years. For 

 a short time the process was discontinued 

 in favor of the Weldon process (of which 

 I have to speak next), but after two 

 years Dunlop's process was taken up 

 again, and, to the best of my knowledge, 

 it is still in operation to this day. It 

 has, however, just like Mr. Dunlop's 

 first chlorine process never left the place 

 of its birth (St. Rollox), although it was 

 for a period of over ten years without a 

 rival. 



weldon's patent process. 



In 1866, Mr. Walter Weldon patented 



