December 11, 1885.] 



SCIENCE. 



525 



fiilly double that obtained in the ordinary way. 

 2. The difficulties to be overcome in the appUca- 

 tion of diffusion are wholly mechanical. 3. The 

 process of carbonatation for the purification of the 

 juice is the only method which will give a limpid 

 juice with a minimum of waste, and maximum of 

 purity. 4. By a proper combination of diffusion 

 and carbonatation, the experiments have demon- 

 strated that fully 95 per cent of the sugars in the 

 cane can be placed on the market either as dry 

 sugar or molasses. 



PROGRESS IN METALLURGY. 



One of the serious metallurgical problems of to- 

 day is the recovery of the by-products from the 

 manufacture of coke by the destructive distilla- 

 tion of bituminous coal. In this country coke 

 for metallurgical purposes is prepared almost ex- 

 clusively either in open heaps or in 'beehive' 

 ovens, — hemispherical fire-brick chambers into 

 which sufficient air is admitted to burn the distil- 

 lates, and thus to produce the heat required for 

 the distillation itself. Not only are the distillates, 

 which contain ammonia and tar, of great value to 

 the color-maker, thus wasted, but, as they burn in 

 actual contact with the coking mass, much (often 

 twenty-five per cent) of the coke itself is inciden- 

 tally burned. Both these evils are completely 

 avoided by coking in retort ovens, heated exter- 

 nally by the combustion of the distillates, but 

 after they have deposited their tar and ammonia 

 in surface condensers. The first volume of the 

 Journal of the Iron and steel institute, for 1885, 

 contains an important group of papers and discus- 

 sions on this subject, whose net result is to place 

 the advocates of retoii; coking in a much stronger 

 position. 



The iron blast-furnace is the chief consumer of 

 coke ; and though in continental European blast- 

 furnaces (and in British foundery cupolas as well) 

 retort coke is as efficient as beehive coke, and 

 though the calorific powers of the two fuels are 

 almost identical, yet in British and American blast- 

 furnaces the efficiency of retort coke has hitherto 

 proved so low as to largely offset the advantages 

 of the retort, — its greater yield of coke and its 

 recovery of by-products. Hence the retort has 

 gained but a slight foothold in these countries, 

 though used on the continent very extensively 

 and successfully with coals of widely varying 

 compositions and properties. We may solve the 

 retort problem either by adapting our retorts 

 to the requirements of our coal, or by adapting 

 our blast-furnaces to the requirements of retort 

 coke. 



Mr. J. Lowthian BeU shows by conclusive ex- 



periments that the low efficiency of British retort 

 coke is due to its ready solubility in the carbonic 

 acid which it encounters on entering the blast- 

 furnace ; and this, in turn, appears to be mainly 

 due to the comparatively low temperature of 

 retort coking. It would seem practicable, how- 

 ever, to raise this temperature approximately to 

 that of the beehive ; and Mr. H. Simon and IVIr. 

 Watson Smith describe the adaptation of the 

 Siemens regenerative system to the retort for this 

 purpose, and the improvement in the quality of 

 the tar which it has effected. The problem of 

 adapting the retort to the coal seems thus in a fair 

 way to solution, while that of adapting the blast- 

 furnace to retort coke appears to be in an equally 

 promising condition, if we may judge from com- 

 parative tests which Samuelson describes, con- 

 ducted on a gigantic scale in his blast-furnaces, 

 themselves highly efficient, in. which British re- 

 tort coke shows an efficiency equal to that of the 

 best beehive coke. This one success outweighs in 

 importance fifty previous failures. 



A very important contribution to the world's 

 supply of tar and ammonia is promised from an- 

 other source. A large and constantly increasing 

 proportion of our metallurgical furnaces are 

 heated by gas produced by the simultaneous dis- 

 tillation and partial combustion of bituminous 

 coal and similar substances. In the apparatus 

 employed the hydrocarbons, etc., arising from dis- 

 tillation, incidentally become diluted with such 

 enormous volumes of nitrogen and carbonic oxide 

 from the partial combustion of the coal, that the 

 condensation of their tar and ammonia would 

 require apparatus of a size and cost which are 

 simply prohibitory ; and, unable to separate these 

 valuable substances, we burn them in enormous 

 quantities. But Mr. John Head describes an egg 

 of Columbus which promises to enable us to 

 isolate the distillates for condensation and the 

 manufacture of niuminating-gas. 



A knowledge of the relations between the 

 chemical composition and the physical properties 

 of iron, which would enable us to infer the latter 

 from the former, would be invaluable : imfoi-tu- 

 nately investigation has thus far only plunged these 

 relations into hopeless confusion. To elucidate 

 the subject, Dr. Hermann Wedding has carried . 

 out extensive and ingenious microscopic studies of 

 the structure of iron. We have not space to an- 

 alyze the results which he here presents, further 

 than to give as a sample his announcement that 

 malleable iron, produced by any fusion process, 

 consists of two distinct components : 1°, minute 

 porphyritically distributed crystaUine particles ; 

 and, 2°, a homogeneous matrix in which they ai'e 

 distributed. 



