69 



in some respects, while that of C . arenosa gives reactions somewhat intermediate 

 between these two. 



The tannin in the bark of C . calcarata, in some of its reactions, approaches 

 somewhat closely that contained in wattle bark, (Acacia spp.'} and in this respect 

 differs from hemlock. \Mth some of the general reactions, however, there is 

 a similaritv \\'ith all three, as thev all belong to the same broad group. The 

 aqueous extracts from the barks of C. calcarata and C. arenosa do not possess the 

 deep red colour usuallv given bv wattle bark containing a similar amount of 

 tannin, and would apparently make a lighter coloured leather. 



Those chemical reactions in which the tannin of C. calcarata resembles 

 somewhat that of wattle bark are the following; (Acacia pycnantha bark 



was taken for comparison) : — 



(rt) When a dilute solution of ferric-alum is added to a very dilute 

 solution of the aqueous extract, in a test tube, and allowed to fall through the 

 solution, a somewhat closeh' agreeing purplish-grey colour is obtained, and 

 eventually a purplish precipitate forms. With both hemlock and C. glaiica 

 this reaction gives a greenish colouration, and greenish-black precipitates. With 

 stronger solutions, C. calcarata gives a greenish-brown colour, and a dark purphsh- 

 grey precipitate. Ferric chloride gives a more marked green colouration \\dth 

 Callitris tannins than that obtained \\ith ferric-alum. 



(h) With sulphate of copper and ammonia in excess, both wattle-bark 

 tannin and that of C. calcarata give dense precipitates, the filtrates from both 

 being bright blue. The copper salt \-\ith hemlock tannin is soluble in an excess 

 of ammonia, and that of C. glauca almost entirely so, the filtrate of the latter 

 being of a purplish-bro\\-n colour if the copper salt is not in large excess. With 

 C. aroiosa the copper salt is only partly soluble, the filtrate being greenish. 



(c' \\'ith a crystal of sodium sulphite on a white tile, the reaction ^^ith 

 wattle-bark tannin and that of C. calcarata are similar; they both give 

 reddish colours at once, in which one drop of dilute ammonia placed near the 

 salt, produces at first a yellow colour, and after some time crimson bands are 

 formed in places. \\'ith hemlock tannin, and \\ith those of C. glauca and C. 

 arcjwsa, the ^^ellow colour is scarcely produced, nor are the crimson streaks 

 obtained, the colour being more of an orange red. 



\Mth the other general reactions Callitris tannins agree with that of hem- 

 lock, and the coniferous barks generally'. Nitrous acid does not give a colour 

 reaction, but only a bro\\TL precipitate. The insolubilit}- of the copper salt in 

 excess of ammonia with C. calcarata, shows the tannin of this tree to differ in 

 some respects from those of the pines generally, and it is the only species of 

 Callitris sho\\ing this reaction so distinctly. 



