OCCURRENCE OF CALCIUM OXALATE IN EUCALYPTUS BARKS. 29 



spp., in certain algae and in other small plants. I cannot 

 find, however, that crystallised calcium oxalate has pre- 

 viously been found occurring in quantity iu the bark of 

 plants belonging to genera which often occur as immense 

 trees, and in this respect, therefore, the Bucalypts are 

 peculiar. Crystals of carbonate of lime (crystoliths) have 

 been found in the epidermis of some plants, as in a few 

 species of Ficus, but the constituents of this salt are not 

 considered to be poisonous. 



The presence of calcium oxalate in quantity in Eucalyptus 

 barks may eventually be found to have some bearing on the 

 formation of the particular tannin present. It has already 

 been determined that in those barks which contain much 

 calcium oxalate the tannin is decidedly superior to that 

 found in species in which the crystals are present only in 

 small amount. Some of these barks should make excellent 

 leather, and the amount of available tannin in some species 

 is considerable. The bark of the "Gimlet," Eucalyptus 

 s ilubris, for example, gave by extraction with hot water 

 30"5°/° of total extract, and lS'C'f of tannin absorbed by hide 

 powder; these were calculated on the air dried bark. The 

 tannin extracts from this class of Eucalyptus barks do not 

 readily decompose or even darken much when evaporated 

 to dryness at the temperature of boiling water, and the 

 manufacture of excellent tanning extracts from Eucalyptus 

 barks is, therefore, possible. 



The amount of calcium oxalate in the bark of E. salubris 

 was 16°/% and it should be possible to profitably extract this 

 from the bark residue, and thus manufacture oxalic acid 

 very cheaply as a by-product. The oxalic acid should also 

 be obtained fairly pure at the first separation, because the 

 other salts and organic substances precipitated at the same 

 time in the alkaline solution, are readily dissolved by acetic 

 acid. Eucalyptus barks rich in calcium oxalate are easily 



