38 GUMS OF EUCALYPTS AND ANGOPHORAS 



examine the " solution " under the microscope, you will see that 

 it is only an emulsion, exhibiting the undissolved resin as minute 

 globules suspended in a watery solution in a manner reminding 

 you much of the milk of animals. Besides, if the emulsion gets 

 cold, the globules crowd together and unite in a bottom sedi- 

 ment, sticky and ductile at first, like cobbler's wax, and finally 

 brittle (as Mr. Staiger says) like shellac. Still there is not the 

 least relation between shellac and this sticky residue, for the 

 latter gets quite soft if only warmed to the temperature 

 of the human body, and besides, if boiled with water, again 

 goes in emulsion, quite as it did before. With methylated 

 spirits, it apparently makes a varnish and a pretty good polish 

 for wood, but keeps soluble in hot water, and is therefore 

 utterly useless. The peculiar smell of the gum of Eucalyptus 

 maculata reminded Mr. Staiger of benzoic acid and induced 

 him to ascribe it to " benzoic acid contained in the gum in a 

 raw state." Still the said gum does not contain the least trace 

 of benzoic acid, as I have proved by my test experiments. The 

 smell itself does not resemble benzoic acid at all, but it reminds 

 one of the liquid styrax used lately in Europe for the cure of 

 itch. The smell sticks to the insoluble part of the gum 'and 

 does not go into the watery solution proper. The latter contains 

 tannic acid (kinotannic acid) in a subordinate quantity, and besides 

 this a very bitter extract Avhich I could prepare by imspissation of 

 larger quantities of the gum solution. In the old times of penal 

 settlements in New South Wales the gums of different ironbarks 

 were brought to Europe under the name of " Botany Bay Kino," 

 and though mostly derived from FAivuhiptm siderophloia are 

 still mentioned in the modern pharmaceutical books as coming 

 from Eucahjptua resinifera, which denomination (now restricted 

 to a different species) waj given by Allan Cunningham to the 

 Eucalyptus siderophloia of the modern botanists. This gum 

 contains a large quantity of arabine, besides a high amount of 

 tannic acid. The solution of it gets more red when a strong 

 acid is added, and more brown when tested with liquor am- 

 monite. The gum of Eucalyjitus siderophloia deposited under 

 the bark and between the layers of the wood, turns after some 

 months into a tough hard substance, quite insoluble in water 

 and quite free from tannic acid. A very fine red gum is yielded 



