68 



Professor Trimble summarises his results in the following- statement : — 



■' These Conifer barks from India have been found to contain tannins 

 identical with those found in the barks derived from the same natural order in 

 America ; therefore, so far as studied geographically, distribution has caused no 

 variation in the tannins of the Conifers." 



Now that most of the Conifer barks of Australia have been investigated 

 this conclusion mav be broadly supported, so far as the general results refer 

 to the Callitris barks. Although there are differences shown by the tannins of 

 the several species themselves, yet, broadly they all agree with the tannin of 

 hemlock, as well as with that of other Coniferous trees of America and India, 

 and mav, therefore, be considered as somewhat closely related to oak-bark tannin. 



The general results obtained from this investigation are most promising, 

 and show that some of the Callitris barks, especially those of C. arcnosa and C. 

 calcarata, have a considerable value as tanning materials. Throughout Australia 

 enormous quantities of Callitris barks are procurable, at present going to waste, 

 which might \\ith advantage be turned to profitable use in the leather industry. 



Besides the local use for the barks themselves, the extensive and increasing 

 demand for tanning extracts in Europe and America, makes the possibility of 

 utilising these vast resources of Callitris barks of Australia, in this direction, 

 almost beyond question, and it may be assumed, that eventually a considerable 

 industry will be established in Australia, in the manufacture of tanning extracts 

 from the Callitris barks. There seems no reason, why, from the barks of these 

 trees, results even more satisfactory than those obtained with hemlock, should 

 not be secured, particularly as some species are so rich in tannin. 



In the " Leather Trades Review " (1899, 32, 542) it is stated, " That tanners 

 allege that i lb. of 'hemlock extract' will go as far as i| lb. of oakwood or 

 chestnut extract, that it will do more work, and will produce i to 2 lb. more 

 leather per hide." The objectionable features ascribed to hemlock, such as 

 those of colour, have been largely overcome in American practice, and little 

 difficulty is now experienced in manufacturing a good leather from it. 



From their chemical reactions it is seen that the tannins of the Callitris 

 barks belong broadly to the catechol group. The reactions which they give with 

 ferric-alum, ferric chloride, and with copper sulphate and ammonia in excess, are not 

 similar with all the species, and these reactions separate somewhat sharply the 

 tannins of two of the most important and, perhaps, abundant species, C. calcarata 

 and C. glauca. The reactions given with the tannin of C . glauca, as well as with 

 that of most of the other species of Callitris, agree fairly well with those given 

 with the tannin of hemlock, but the tannin of C. calcarata differs from thesQ 



