252 REPORT— 1901. 



It has been long recognised that the study of hydrolysis affords the 

 best means of estimating the strengths of very weak acids and bases. 

 (Since the affinity constant of pure water is now known with considerable 

 certainty, exact measurements can be made in this way, even when the 

 free acids or bases are difficultly soluble in water. It would, for instance, 

 be possible to make exact determinations of the effect of substituents on 

 the strength of phenol and aniline. The influence of constitution on the 

 affinity constants of these very weak electrolytes would form an interesting 

 held for research. 



Tlie Relative Progress of the Goal-tar Industry in England and Ger- 

 many dvrlnq the past Fifteen Years. Bij ARTHUR G. GreeN, 

 F.I.'C., F.G.'S. 



[Ordered by the Council to be printed i>i extenso.'] 



The coal-tar colour manufacture has well been called the flower of 

 the chemical industries. Although in absolute money value of its pro- 

 ducts not equalling some other branches of industrial chemistry, it repre- 

 sents the highest development of applied chemical research and chemical 

 engineering, and may well be taken as the pulse of the whole chemical 

 trade. Indeed a country which allows the most scientific branch of 

 chemical industry to languish cannot expect to maintain pre-eminence 

 for long in any simpler branch of chemical manufacture ; since the skill 

 trained for attacking the difficult problems of organic chemistry is certain 

 sooner or later to be brought to bear on the simpler questions presented 

 in the manufacture of so-called ' heavy ' chemicals (acids, alkalies, bleach, 

 salts, Ac), and processes hitherto often left to the supervision of foremen 

 will be taken in hand by educated chemists, with consequent improvement 

 in methods of manufacture, better yields, purer products, and cheaper 

 production. The importance of the coal-tar industry cannot therefore 

 be estimated alone by the value of its products, for it exerts a wide- 

 spread effect upon all other branches of chemical manufacture, from 

 many of which it draws its supplies of raAv material. As a pregnant 

 example of this influence, especially noticeable during the last decade, 

 I may mention the revolution which is taking place in the manufacture 

 of sulphuric acid, that most important product of the ' heavj' ' chemical 

 ti'ade. A strong demand had arisen in the colour industry for a large 

 and cheap supply of sulphuric anhydride, chiefly in connection with the 

 manufacture of alizarine colours and of artiflcial indigo. With the object 

 of satisfying their own requirements in this respect, the Badische Aniline 

 and Soda Works of Ludwigshafen devoted much time and research to the 

 problem of improving the catalytic process usually known by the name 

 of Winckler, a modification of which process had been worked in this 

 country by Squire Chapman and Messel since 1876. This endeavour was 

 attended with such success that by means of the process and plant which 

 they finally evolved they were enabled to produce sulphuric anhydride 

 so cheaply that not only could it be used as such for a large variety of 

 purposes, but by combination with water afforded a profitable source of 

 sulphuric acid. This new method of manufacturing sulphuric acid is, for 

 concentrated acid at least, cheaper than the chamber process ; and since 

 the product is absolutely free from arsenic, and can be produced at any 

 desired concentration, it seems likely to supplant eventually the time- 

 honoured method of manufacture. 



