A NEW METHOD OF ASSAYING TANNATES. 



By Dp. JOSEPH LAUTERER. 



[Read before the Royal Societij of Queensland, Fehniarij 16, 1895.'] 



A GREAT number of methods have been described for determining 

 tannin and assaying tannin-yielding materials. All of them are 

 tedious and require some hours, and at the end do not give 

 satisfactory results. For the chemist or the tanner, who wants 

 to buy some material, a quick method of ascertaining the actual 

 amount of tannates for which he has to pay, would be invaluable. 

 For the scientific investigator of the imperfectly-known con- 

 stituents of a flora, who has to go through a large number of 

 plants, and who is often travelling, the published methods are 

 nearly or altogether unavailable. I therefore put before the 

 public to-day a colorimetric process of assay, which is very 

 delicate and gives satisfactory results in less than five minutes 

 if everything is prepared. 



I. — Preliminary Arrangements. 



(1) In a six-ounce bottle two drops of liq. ferri perchloride 

 fort, of the British Pharmacopoeia are dropped and diluted with 

 3 ounces of distilled water, 1 drachm of Mistura Acaciae 

 (mucilage of arabic gum) is added, the whole well shaken and 

 the six-ounce bottle is then filled with distilled water. 



(2) A 1 per mille and a 1 per cent, solution of the best 

 Berlin tannic acid (Schering's) in distilled water is then prepared 

 and filled in well-made patent drop bottles. 



(3) A number (50-60) of 1-drachm Nessler bottles (perfectly 

 clean) are kept ready. 



One drop of the -001 solution of tannic acid is then 

 put in the first Nessler bottle and the bottle filled with the 

 solution of perchloride of iron mentioned under (1). This Nessler 

 bottle IS labelled " 1 per mille." 



