Dyes and Tans. 



426 



[November, 1908. 



Temperature 

 at which ex- 

 traction is 

 conducted. 



Tannin. 



Non- 

 Tannin. 



Percentage 

 of Tannin on 

 maximum. 



\J\)l\JWt Ol T 



solution in 

 Red. 



JJtJI LcUu. 



\ inch cell. 

 Yellow. 



Percentage 



/if nnlniu 1 

 y)L LUXUUL 



on maxi- 

 m um. 



C. 



Per cent. 



Per cent. 





Degrees 



Degrees. 



- 



15 



21 '2 



11 '6 



66 *2 



2*6 



4*1 



51*1 



15-30 



29*0 



A .O 



y*8 



90 "6 



3 - 



4'1 



54.2 



OA A A 



30 '1 





94 - 



3*0 



4.4 



56*5 



40-50 



30 - 2 



y 8 



944 



3*1 



5 



61*8 



50-60 



30 '4 



1 A ■ A 



10 4 



95 - 



3-9 



6-5 



79*9 



60-70 



31-5 



10-6 



98-4 



4-2 



6-5 



81-6 



70-80 



32 "0 



1 A.O 



10 8 



100 '0 



4 '2 



7'0 



85*5 



80-90 



30-8 



11-2 



96-2 



4-9 



7-4 



93-8 



90-100 



30-1 



11-8 



94.0 



53 



7-8 



100-0 



boiled 



29-4 



12-0 



91-8 



5-7 



7-2 



98-4 



1 



Decolorisation.— As in the case of most 

 extracts, it is probable that wattle 

 extract will generally be improved by 

 decolorisation. The agent usually 

 employed for this purpose is dried 

 blood, but plates of blood-albumen, 

 alumnia, and casein are also occa- 

 sionally used. 



The blood or albumen is dissolved in 

 a little water, added to the vat liquor 

 obtained as described above, and well 

 mixed. On raising the temperature to 

 70 degrees C, the albumen coagulates 

 and carries down much of the colouring 

 matter, which is allowed to settle, 

 after which the clear liquid may be 

 drawn off for evaporation. 



Decolorising always occasions a certain 

 loss of tannin, and for this reason is 

 dispensed with when not absolutely 

 necessary. Sulphurous acid is fre- 

 quently used to " brighten " tan liquors, 

 but its use should be unnecessary in 

 preparing wattle bark extract; it is 

 said to be disadvantageous in various 

 ways. 



Concentration of the Liquor.— The 

 liquors from the leaches or decolorising 

 vats are concentrated by evaporation. 

 Up to a certain stage it is possible to 

 use for this purpose '' spray " machines 

 of the Yaryau type, which concentrate 

 the liquid with as little access of air 

 and at as low a temperature as possible. 

 This result is obtained by passing the 

 liauid into copper tubes working under 

 reducing pressure and kept at the 

 required temperature. The fluid is 

 immediately converted into spray and 

 swept forward into a separating cham- 

 ber. In this way the liquid can be 

 concentrated up to a specific gravity 



of 1"1 to T2 without having been heated 

 above 70° C The final evaporation of 

 the extracts is conducted in ordinary 

 vacuum pans. It must be understood, 

 of course, that in all stages of its 

 manufacture the extract must be kept 

 from contact with iron. The apparatus 

 is usually constructed of wood and 

 copper. 



In the foregoing account of extract 

 manufacture an outline of the process 

 only has been attempted, and for 

 fuller details both of the process and 

 of the plant required. Prof. Proctor's 

 handbook alreadv referred to might 

 be consulted with advantage. 



Considerable quantities of wattle 

 extract are already manufactured in 

 Australia for its preparation, chiefly 

 from branch bark, which is too small 

 to pay for stripping. A fluid extract 

 is prepared which contains 60 per cent, 

 of water and about 38 per cent, of 

 soluble tannin. Practical experiments 

 are also being conducted in Australia 

 with a view of the preparation of a 

 tanning extract from wattle leaves. It 

 is probable that where wattle bark 

 extract manufacture is contemplated 

 it would be advantageous to adopt the 

 plan of building a central extract 

 factory, conveniently situated with 

 respect to a group of plantations, the 

 produce of which could be worked up 

 in the factory. This plan has been 

 worked successfully in Germany in the 

 manufacture of beet sugar, and more 

 recent instances of its success are the 

 central ginnexies for treating seed 

 cotton in West Africa and the West 

 Indies and elsewhere. — Bulletin of the 

 Imperial Institute, Vol. VI. No. 2, 1908. 



