28 ON SOME N.S.W. TAN-SUBSTANCES. 



to determine the amount of tanning principle in those barks which 

 do not contain it in sufficient abundance for the purposes of the 

 tanner ; we shall thus know which to avoid. As regards the kinos, 

 although they are usually rich in tannic acid, they will probably 

 come into extensive use in the future in medicine, and as ingredients 

 in pigments and coloured varnishes &c, rather than as tans, for 

 they usually make but indifferent leather. 



Dates. — Notwithstanding the well-known facts, (1) that in most 

 cases, barks, especially those from species of Acacia, improve in 

 tanning power if they are properly stored for a period, and (2) 

 that after a further more or less variable period they diminish in 

 tanning power, — it has not been the practice, as far as I am aware, 

 to give dates with analyses, in order to make them comparable 

 with others. I propose in every instance not only to give the 

 dates of collection of the substances analysed, but also of the 

 analyses themselves. This, in my humble opinion, is a matter of 

 the highest importance. (Experiments giving the percentages of 

 tannin in the same bark at regular intervals, will of course take 

 years to complete). 



In the case of kinos, it is very desirable to know approximately 

 the dates at which they were exuded. The present samples were 

 all fairly new, with the exception of that of E. siderophloia, when 

 collected ; I can state nothing more definite in these instances. 

 Kinos while attached to the trees are liable to alteration, firstly, 

 from rain, which washes out more or less of their soluble 

 constituents, and secondly, from the air, as under its action they 

 tend to become insoluble ; for instance, some kinos which are freely 

 soluble in water become more or less insoluble in that liquid, and 

 even insoluble in alcohol. 



Species Names. — Fully sensible that if there be the slightest 

 doubt as to the identity of any species an analysis may be even 

 worse than useless, as it may be misleading, every care has been 

 taken to ensure perfect accuracy in the names of species. 

 Flowering or fruiting specimens (or both) have been taken in each 

 case. Specimens from the exceedingly difficult genus Eucalyptus 

 have in all cases been referred to Baron Mueller for determination 

 or confirmation, and I take this opportunity of expressing my 

 indebtedness to him. 



Allowance for Moisture. — The percentages of tannic acid and 

 extract have in all cases been determined upon substances 

 thoroughly dried at 100° C. The amount of moisture in freshly 

 stripped bark (as compared with bark dried at 100° C.) may, for 

 practical purposes, be assessed at from a quarter to one-third of 

 its weight. 



Selection of Samples. — Of the kinos I have had from 3 to 4 Tbs 

 of each to select from. From each parcel I have endeavoured to 



