Hartley — On a Violet Colouring -Matter, ^-c. 65 



to stand for two or three days, and afterwards decanted or pipetted off, 

 leaving about 10 c.c. of solution. This last part sometimes contained a 

 deposit of dead bacteria and other matter which had siphoned over. 



A part of the clear violet solution was now tested for starch, a possible 

 impurity from the potato, with a negative result. The solution was then 

 evaporated down to dryness, partly on a water-bath and partly in vacuo ; when 

 dry it was a dark blue, almost black in mass, amorphous solid. It dissolved 

 readily in cold alcohol, giving a violet solution, and in ether a purple solution, 

 as also with chloroform. A volume of 1'5 c.c. was placed in each of the ten 

 tubes, and tested with the following reagents : — 



To No. 1 was added 0'5 c.c. of Normal KOH. The colour changed to blue, 

 to green, and then to yellow. 



To No. 2 was added 0'5 c.c. NajCOj Normal. The colour changed to a dark 



blue. 

 To No. 3 was added O'l c.c. " Concentrated " H2SO4. The colour changed 



to green. 

 To No. 4 was added 0'3 c.c. " Concentrated " H2SO4. The colour changed 



to yellow. 

 To No. 5 was added 0'2 c.c. HNO3 " Concentrated." The colour changed 



to yellow. 

 To No. 6 were added 2 drops of strong Ammonia. The solution was 



immediately bleached ; the addition of acetic acid failed to restore 



any colour. With dilute Ammonia it turned green before bleacliing. 

 To No. 7 was added a drop of bromine water. Colour instantly destroyed. 

 To No. 8 was added 0'5 c.c. H2O2. An opalescent blue, possibly due to 



partial precipitation of the colouring matter by water. 

 To No. 9 was added 0'5 c.c. SnClj. Gives a colourless solution on standing. 

 To No. 10 was added 0'5 c.c. ether. Gives a purple tinge to the alcoholic 



solution. 



The pigment will act as an indicator to acids if sufficient alkali be present 

 to turn the violet solution blue. The addition of acids turns it green, as, for 

 example, weak hydrochloric acid. If an ethereal chloroform or alcohol 

 solution be evaporated from a test-tube, the dissolved pigment will precipitate 

 on the glass and show the same colour as the solution from which it pre- 

 cipitated. Some 20 c.c. of the alcoholic solution were poured through a 

 column of precipitated chalk, in the hope that if two pigments were present 

 they would separate, but this did not occur. 



In order to test the dyeing properties of the colouring-matter, some 

 20 C.C. of the alcoholic solution (containing 0-02 grms. solid) were placed in a 



e2 



