190 



SCIENCE 



[N. S. Vol. XL. No. 1023 



when cMorine was manufactured exclu- 

 sively by means of hydrochloric acid, this 

 would have sounded like a paradox. 



The consumption of chlorine for the 

 preparation of organic chlorination prod- 

 ucts utilized in the dye-stuff industry, is 

 also increasing continually, and its use for 

 the manufacture of tetrachloride of carbon 

 and so-called acetylen chlorination prod- 

 ucts, has reached quite some importance. 



There is probably a much overlooked but 

 wider opening for chlorinated solvents in 

 the fact that ethylen-gas can be prepared 

 now at considerably lower cost than ace- 

 tylen, and that ethylen-chloride, or the old 

 known "Dutch Liquid," is an unusually 

 good solvent. It has, furthermore, the 

 great advantage that its specific gravity is 

 not too high, and its boiling point, too, is 

 about the right temperature. It ought to 

 be possible to make it at such a low price 

 that it would find endless applications 

 where the use of other chlorination solvents 

 has thus far been impossible. 



The chlorination of ores for certain 

 metallurgical processes may eventually 

 open a still larger field of consumption 

 for chlorine. 



In the meantime, liquified chlorine gas, 

 obtained by great compression, or by in- 

 tense refrigeration, has become an impor- 

 tant article of commerce, which can be 

 transported in strong steel cylinders. Its 

 main utilization resides in the manufacture 

 of tin chloride by the Goldschmidt process 

 for reclaiming tin-scrap. It is finding, 

 also, increased applications as a bleaching 

 agent and for the purification of drinking 

 water, as well as for the manufacture of 

 various chlorination products. 



Its great handicap for rapid introduction 

 is again the question of freight, where 

 heavy and expensive containers become in- 

 dispensable. 



In most cases the transportation prob- 



lem of chlorine is solved more economically 

 by handling it as chloride of lime, which, 

 after all, represents chlorine or oxygen in 

 solid form, easily transportable. 



It would seem as if the freight diffi- 

 culty could easily be eliminated by produc- 

 ing the chlorine right at the spot of con- 

 sumption. But this is not always so simple 

 as it may appear. To begin with, the cost 

 of an efficient plant for any electrolytic 

 operation is always unusually high as com- 

 pared to other chemical equipments. Then, 

 also, small electrolytic alkali plants are 

 not profitable to operate. Furthermore, 

 the conditions for producing cheap chlorine 

 depend on many different factors, which 

 all have to coordinate advantageously; for 

 instance, cheap power, cheap fuel and 

 cheap raw materials are essential, while, 

 at the same time, a profitable outlet must 

 be found for the caustic soda. 



Lately, there has been a considerable 

 reduction of the market price of caustic 

 soda; all this may have for effect that the 

 less efficient electrolytic processes will grad- 

 ually be eliminated; although this may not 

 necessarily be the case for smaller plants 

 which do not compete in the open market, 

 but consume their own output for some 

 special purpose. 



Several distinct types of electrolytic cells 

 are now in successful use, but experience 

 seems to demonstrate that the so-called 

 diaphragm cells are cheapest to construct 

 and to operate, provided, however, no 

 exception be taken to the fact that the 

 caustic soda obtained from diaphragm 

 cells always contains some sodium chloride, 

 usually varying from two to three per 

 cent., which it is not practical to eliminate, 

 but which for almost all purposes does not 

 interfere in the least with its commercial 

 use. 



Mercury cells give a much purer caustic 

 soda, and this may, in some cases, compen- 



