.380 REPORT— 1893. 



Oxyquiiione Colours. 



5. Alizarin Red (alumina mordant). 

 10. Alizarin Turkey Red (cotton). 



Natural Colouring Matters. 



6. Madder red (alumina mordant). 



1. Cochineal scarlet (tin mordant). 



2. Kermes scarlet (tin mordant). 



Silk Patterns. 



The foregoing colours were dyed on silk, employing 2 per cent, 

 •colouring matter, and the patterns were exposed to light, along with 

 those on wool, with the result that the relative fastness of the various 

 colours was practically the same as on wool. 



General Result. 



The experiments extend at present over too limited a number of 

 colouring matters to enable one to draw fixed general conclusions, but it 

 may be well already at this point to record the following observations. 



The most fugitive reds on wool and silk are the eosins and allied 

 colours. Curiously enough, the introduction of the methoxy group, as in 

 methyl-eosin, &c., increases the fastness, not of the colour as a whole, but 

 of the pale faded tint which results after the first few weeks' exposure. 

 As already stated, this tint remains practically unchanged even after a 

 whole year's exposure. This is specially noticeable on the silk patterns. 



With respect to the rosindulines, it is interesting to note that the 

 G shades are very fugitive, while the B shades are moderately fast. 



All basic reds belong to the more or less fugitive class, including, 

 namely, the magentas, safranines, and rhodamines. The nature of the 

 acid with which the colour base is combined seems to have no influence 

 upon the fastness of the dyed colour. 



Comparatively few (about twenty) of the azo reds examined are 

 fugitive, and these belong chiefly to the simple monazo colours. 



The great bulk of the fast and moderately fast reds belong to the azo 

 colours, the so-called secondary disazo colours being generally faster than 

 the rest. It is evident, however, that the fastness of these azo colours 

 depends, not only upon the base which is azotised, but also upon the 

 character of the naphthol-sulphonic acid employed. This is especially 

 noticeable in the chromotropes, in which a particular dioxynaphthalene 

 disulphonic acid is employed, and all of which are remarkable for their 

 fastness. The particular azo compound and phenol united together is 

 also of importance. 



With respect to the milling and cloth reds, it does not appear that the 

 use of mordants with them increases their fastness to light. 



The number of very fast reds is extremely limited, but it includes both 

 natural and artificial dyes — namely, madder, cochineal, kermes, alizarin, 

 and the chromotropes 2 R and 2 B. When it becomes possible to expose 

 the Congo reds, one or two others will no doubt have to be added to the 

 list of very fast artificial red dyes. In this connection it may be pointed 

 out that certain reds obtained from the natux'al dye-stuff's are fugitive, 

 namely, those obtained from Lima-wood, Cam- wood, and the allied woods. 



It is well to add that there are no sharp lines of division with respect to 



