162 MR. E. R. WATSON ON 



The change of shade from orange to pink, which was noted in the case of latkan 

 dyeings on cotton, was scarcely noticeable on silk. 



It is interesting to note the irregular way in which the nature of the textile 

 material affects the fastness of the dyeings. Thus in the case of palas, latkan, 

 manjista and primuline developed with p-Naphthol the dyeings on silk are faster to light 

 than the corresponding dyeings on cotton ; but the reverse is true for safranine and for 

 primuline developed with phenol. 



(II). Fastness to washing with soap. 



The samples were treated in the same way as were the cotton samples previously, 

 i.e., they were all steeped for 15 minutes at 6o°C. in an aqueous solution of neutral 

 soap containing 15 gms. per litre, 250 cc. of solution being used for 1 gm. of silk. 

 The results are recorded in Table II ; and here again the groups are identical with 

 the corresponding groups into which cotton dyeings were classified in the previous 

 paper. As a result of experience gained in examining the cotton dyeings, it was 

 considered advisable to make a further set of observations, viz., as to the tendency of 

 the dyed cloth to stain a piece of white cloth placed in contact with it in the soap- 

 bath. It was found that there was a tendency to over-rate the fastness of dyeings 

 of a full shade and to under-rate the fastness of dyeings of light shades. The reason 

 for this is fairly obvious : a deep shade can lose a considerable amount of colouring 

 matter and still not be rendered relatively much lighter than the original shade, 

 whereas the loss of even a smaller quantity of colouring matter from a light shade 

 would be very noticeable. On the other hand the sample losing the large amount of 

 colouring matter would be more likely to stain white fabrics in contact with it in the 

 soap-bath. (The problem, it is true, is complicated by the fact that the extent to 

 which the white fabric would be stained would depend not only on the amount of 

 dyestuff brought into solution in the bath, but also on the nature and preliminary 

 treatment of the white fabric). An equal weight of pure white silk cloth was folded 

 and loosely knotted together with the dyed sample before entering in the soap-bath , 

 and after the 15 minutes' treatment in the bath the previously white piece of cloth 

 was rinsed, dried and examined. The scale employed to indicate the extent of the 

 marking is (1) not marked; (2) scarcely marked ; (3) slightly marked ; (4) considerably 

 marked ; and (5) much marked. 



These observations show that the majority of dyeings with synthetic dyestufls 

 do not stand soaping at all well, and in this respect the indigenous dyes manjista, 

 bakam on tannin-iron mordant, lac and kamala compare very favourably with the 

 synthetic products. 



(III). Fastness to Alkali. 



Determined as in case of cotton dyeings, i.e., samples were all steeped for 

 10 minutes in a solution of sodium carbonate (10 gms. cyst, carbonate per litre) at 

 6o°C, washed, dried and compared with original. For 1 gm. of cloth 250 cc. of solution 

 were used. The groups into which the dyeings are classified are identical with the 

 corresponding groups for cotton dyeings. 



