we He eS Se ee 
THE UTILIZATION OF LEATHER WASTE. 
Chrome alum can also be made from the recovered chromium from 
a chrome leather, and mention is made of this in Wolff’s German patent. 
. ‘The chrome leather is dissolved in 5 per cent. H,SO, by heating to 
80-90° G., and fat separating out being recovered, although in the 
writer’s opinion it would be better to treat de-greased leather, as a 
better yield of fat would be obtained, and the subsequent processes made 
cleaner. From the solution the chrome, together with the SO,, &c., are 
precipitated by adding an excess of lime. This precipitate is next. re- 
dissolved in a definite quantity of sulphuric acid and potassium sulphate, 
and from this solution, after clarifying and concentrating, the chrome 
alum is allowed to crystallize out. 
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The glue liquor is freed from any excess of lime by a current of CO). 
‘The following quantities given will indicate the approximate amounts 
to use, but it is reasonable to suppose that the final yield of chrome 
alum will depend upon the chrome content of the leather :— 
600 lb. leather cuttings. 
2,000 lb. 5 per cent. H,SO,. 
Precipitated chrome sludge treated with— 
. 40 Ib. potassium sulphate. 
| 600 Ib. of 5 per cent. H,SO,. 
Yields of finished products— 
: About 150 Ib. glue, 
About 180 Ib. chrome alum, 
or, in other words, 50 per cent. and 60 per cent. respectively on the 
weight of leather used. 
The novel use of enzymes in the preparation of hide glue from. 
waste is mentioned in Rohms’ German Patent No. 303,184. The waste. 
leather is first treated with a dilute solution of caustic soda, and the 
residue subjected to a further treatment with the enzymes of the pan- 
ereatic juice. In order to prevent any actual decomposition of the 
hide during this digestion, addition is made of such materials as 
ammonium salts, amino acids, or some other type of protein degradation 
products which act in the manner of an inhibiting agent. : 
et 
Manvracturr or Lratruer Boarps. 
Having mentioned a few of the patents concerning the preparation 
of glue, attention will now be turned to those connected with leather 
substitutes and boards. Needless to say, the composition of these 
“substitutes varies very much, and almost anything can be used in con- 
junction with the leather to act as a filling or binding agent. One of © 
the usual constituents is rubber, either new or strap stuff, in which cases 
the mixture is usually submitted to a vuleanizing process. Thus W. S. 
Smith in his specification uses 60 parts of reclaimed rubber, 30 parts 
of leather waste, and 10 parts of*ground-up outer covers of tyres. 
Sulphur is subsequently added together if necessary with some blown 
oil and any fibrous material available. The whole is finally vulcanized. 
_ The product can be used as a sole leather substitute, for floor coverings, 
pump discs, and crutch shoes. 3 
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