PROCEEDINGS OF SECTION B. 109 



The staining of the wool is therefore not due to the acetic acid 

 used as a preservative. 



The remainder of the sample No. 5 was sterilized by heating, 

 and placed in a tightly-stoppered bottle. 



It was thought that the colouring matter causing the stain might 

 be due to some material obtained from the residue after the juice had 

 been expressed. To test this, 25 grams of the residue after sample 

 No. 5 had been expressed were placed in 100 c.c. water, 5 c.c. concen- 

 trated acetic acid added, a piece of wool introduced, and the whole 

 treated in the usual way. The final wool was stained like that from 

 the original sample No. 1, but of a deeper-brown tint. 



The colouring matter which produces the stain can therefore be 

 obtained from the residue of the raspberries after the juice has been 

 expressed. It is possible, therefore, that the stain may be obtained if 

 the raspberries are left in contact with the juice for any length of time. 

 In the last experiment the residue was in contact with the hot 5 per 

 cent, acetic acid for one hour, a far more severe test than the residue is 

 likely to undergo in the practical extraction of the juice. 



It was also found that raspberry juice on allowing to stand and 

 ferment produced a brown stain on the final wool. In order to test 

 this, sample No. 3, which had been sterilized and found to give no 

 reaction with the wool test, was allowed to stand in an open vessel 

 and ferment until the colour had nearly disappeared, 50 c.c. were taken 

 and tested as usual. The final wool was stained brown. This would 

 account for the stain given by sample No. 4, to which no preservative 

 had been added, and in which some decomposition might have occurred. 



Fifty c.c. of the sterilized sample No. 5 were allowed to stand in 

 contact with 10 grams of the residue for sixteen days, the solution 

 poured off and tested as usual. A deep-brown stain was produced on 

 the final wool. In this experiment both causes might be acting 

 together, viz., decomposition of the juice and extraction of the 

 colouring matter from the residue. 



To test if water alone would extract the colouring matter from the 

 residue, 25 grams of the residue from sample No. 5 were boiled with 

 100 c.c. of water for one hour, filtered, and the solution tested. The 

 final wool was stained brown. Water alone will therefore extract the 

 colouring matter which causes the brown stain. 



Cold water was next tried, 25 grams of the residue being allowed 

 to stand in contact with 100 c.c. of cold water for two days, and the 

 solution tested. Only a slight brown stain was produced. Cold water 

 therefore does not extract the colour to any extent. 



To confirm these results, another sample of raspberries was 

 obtained from Tasmania from a different source and the juice expressed 

 eleven days, approximately, after picking. The raspberries arrived in 

 a pulpy condition, and all the juice was expressed by hand, no further 

 quantity being obtained by screw pressing (sample No. 6). 



