124 PROCEEDII^GS OF SECTION B. 



bark. The tannin of the " gimlet " is but little decomposed on 

 evaporation, so that no difficulty should be experienced in preparing a 

 good tanning extract with it. But there is another substance found in 

 " gimlet " bark, as well as in the barks of other species, which as a 

 by-product is w^orthy of some consideration : this is oxalic acid. The 

 large amount of oxalate of lime occurring in the barks of some of these 

 species is remarkable, and no less than 16 per cent, of this substance 

 was found to be present in the air-dried bark of Eucalyptus salubris. 

 From an analysis of " gimlet " bark, it was found that there was 

 present in the sample an equivalent to 416 lbs. per ton of an excellent 

 tannin, and 358 lbs. of calcium oxalate, containing theoretically 

 308 lbs. of oxalic acid. It is thus seen that after the extraction of the 

 tannin about one-fifth of the remaining residue of " gimlet " bark was 

 oxalate of lime. The increasing demand for tanning materials makes 

 the preparation of tanning extracts from the numerous astringent 

 substances of Australia a proposition worthy of serious attention, 

 and I am hoping to see an industry for this purpose estabbshed here. 

 Any accompanying material of possible commercial value would then 

 assist the undertaking, and help to make it profitable. In this 

 connexion it might be possible to utilize the sawdust of certain 

 eucalyptus timbers if obtainable in svifficient quantity. I have found 

 that as much as 10 per cent, of tannin is present in the timbers of 

 some eucalypts, and it is desirable that the astringency values of those 

 of other species of the right class should ^be determined, neglecting the 

 " peppermint," the stringybarks, and the " ironbarks, " as the tannin 

 in these groups is not promising for leather manufacture. 



In the leaves of certain species of eucalyptus a dye material exists 

 in considerable quantities. This substance, which has been named 

 myrticolorin, is a glucoside of quercetin, and breaks down on hydrolysis 

 into glucose, rhamnose, and quercetin. Its presence in the leaves of 

 certain eucalypts imparts to them a yellow appearance as they dry, 

 and it may readily be extracted from the finely-ground leaves by 

 treating them with boiling water and filtering boiling hot. Myrti- 

 colorin is fairly soluble in hot water, but little soluble in cold water, so 

 that it separates out as the water cools; it can then be filtered off, washed 

 with cold water, and dried. In the leaves of the " red stringybark " 

 (Eucalyptus maororhyncha) it occurs in such quantities that no less 

 than 8J lbs. of dry myrticolorin have been extracted from 100 lbs. of 

 powdered material, and it probably occurs in even larger amount in 

 the leaves of other species. It is one of a numerous group of dye 

 substances occurring in plants, some of which are used for dyeing even 

 to-day, while at one time they were used in very large quantities. 



Although it is doubtful whether myrticolorin could be profitably 

 extracted to be sold as such; yet, as the raw material for the preparation 

 of quercetin, it shows considerable promise, providing a demand for 



