266 ANIMAL PROTEINS 



of contract " exact and regular working, strict cleanliness, 

 observance of temperatures and other physical data, and 

 scientific supervision, are clearly necessary. " Rule of 

 thumb " is never quite certain to produce the same article 

 twice. In past years British methods of manufacture 

 have been far too empirical. As in other industries, " rule 

 of thumb " must inevitably be replaced by scientific prin- 

 ciple. The advances in colloid chemistry of this last 

 decade or so have, in the author's opinion, supplied the clue 

 to this line of development. In the preceding pages em- 

 phasis as been laid upon the importance of the adsorption 

 law, the lyotrope series, and the valency rule. The manu- 

 facturer or supervisor who understands and can apply 

 these generalizations will find his task vastly easier and 

 his factory more efficient. Much remains to be learnt, 

 however, and the industry would certainly benefit by 

 research work, for which there is a fertile field. 



There is also considerable room for improvement in the 

 methods of chemical engineering usually employed. Whilst 

 the heat engineers have certainly done much to solve the 

 question of evaporation and drying, there is still great scope 

 in the more economical application of heat in extraction, 

 and the last word can hardly have been said on the problem 

 of clarification and decolorization. There is indeed almost 

 as much scope for research by the chemical engineer as by 

 the colloid chemist. 



The industry also exhibits, in common with the leather 

 and many other trades, the same tendency to save labour, 

 both by careful arrangement of the factory and by the 

 installing of mechanical labour-saving devices. Thus, lifts, 

 runaways, hoists, trucks are increasingly used to move the 

 solids, and pipes and pumps to move the liquors. As ever, 

 there is scope for the mechanical engineer. 



If some of these problems are vigorously tackled during 

 the present reconstruction period, there is little doubt that 

 the gelatine and glue industry will be in a much better 

 position to cope with all possible competition in the future. 



From what has been said in Section VIII. as to the wide 



