July, 1912.] 



19 



Dye Stuffs. 



mate of 40,000 lb. per acre for /. arrecta 

 planted through young rubber does not 

 appear to be excessive. 



On the supposition that financial de- 

 tails turn out satisfactory, indigo would 

 certainly seem to be a suitable eatch crop 

 in a young rubber plantation, whilst 

 there may also be possibilities in connec- 

 tion with tea estates in the low country. 

 The Botanic Department of Ceylon and 

 the Agricultural Department of the 

 F.M.S. have repeatedly recommended 

 the growth of other leguminous plants 

 of similar habit as cover crops and green 

 manures in young rubber, whilst green 

 manuring in tea has become an estab- 

 lished practice in Ceylon. The seet 

 from the manufacture of indigo, well 

 rotted and returned to the soil, can 

 scarcely be of less value than the green 

 material directly mulched. In addition 

 to this there is the indigo, which may or 

 may not turn out a commercially success- 

 ful proposition. On this point we are 

 not yet in a position to form a definite 

 opinion. We can only quote the esti- 

 mates given by Baron Schrottky, and 

 leave in his hands the demonstration of 

 the commercial success of his process in 

 Ceylon. Meanwhile a brief description 

 of the process of indigo manufacture as 

 carried out at Lagos estate may not be 

 without interest to our readers. 



An average of 3 feet length (leaves and 

 stalks) of the plants is cut off with a sharp 

 knife or sickle and carried to the factory 

 and evenly stacked in the steeping vats — 

 concrete tanks about 15 feet square and 

 5 feet deep. The plants are kept down 

 firmly by bamboos and iron girders, and 

 water is admitted from a tack at a 

 higher elevation until the green material 

 is entirely covered. The plants are then 

 allowed to steep for about 16 hours, 

 when a first liquor is taken off while a 

 fresh supply of water is run in and fer- 

 mentation is allowed to continue for 4 

 to 6 hours more. We were told chat the 

 time during which steeping could be 

 allowed to continue without putrefaction 

 setting in had been nearly doubled by 

 the addition of a particular substance 

 known as glucosode— a discovery of 



Baron Schrottky's— in certain propor- 

 portions, the result being an increased 

 yield of indigo. A special method is 

 adopted to allow of a second steeping. 

 The water containing the extracted 

 indigo in a soluble iform is run off 

 through a series of perforated tubes laid 

 at the bottom of the vat and at the same 

 time is evenly replaced with clean water 

 from above, so that the access of air to 

 the steeped plants is prevented. If air 

 is once admitted to the fermenting plant 

 no further development of dye can take 

 place. 



From the steeping vat the yellow 

 liquor is run into a circular beating vat 

 at a lower level. The beating, as we 

 saw it, was done by coolies, but on a 

 larger ecale much labour will doubtless 

 be saved by the use of machinery. 

 Special chemicals are introduced at this 

 stage also to facilitate the conversion 

 of the soluble form of the dye into the in- 

 soluble dark blue precipitate of actual 

 indigo, a result which is largely due to 

 bacterial action. The completion of the 

 process is ascertained by a chemical test 

 applied to the clear filtered liquor. 

 When no further precipitate can be 

 obtained, the indigo is allowed to settle 

 at the bottom of the vat and the super- 

 natant liquid is run off. The indigo is 

 washed with clean water and again 

 allowed to settle. The residual blue 

 mud is then pumped on to a filtering 

 table— a skeleton tank built of slats of 

 wood and covered with a eheet of can- 

 vas in which the paste is allowed to 

 drain, the clear liquid passing through 

 the canvas while the indigo is left be- 

 hind. The thick paste is next trans- 

 ferred to a press— a wooden box the 

 bottom and walls of which are perfor- 

 ated with numerous holes. The interior 

 is lined with damp cloth and the paste ia 

 poured in to a depth of 12 or 14 inches. 

 The cloth is carefully folded over the 

 paste and the lid of the box, which fits 

 the interior accurately, is put on. 

 Pressure is applied by means of screws 

 which are tightened at intervals for 

 some hours until the bulk of the paste is 

 reduced to rather more than a third of 

 its original volume* 



