420 Mr. Armit and Dr. Harden. Estimation of [Dec. 5, 



lack of experimental detail, Buchner and Antoni imagined that in our 

 comparative experiments the concentration of glucose and of enzyme had 

 not been kept constant, and ascribed part of the increase produced by boiled 

 juice to the favourable effect of a diminution in the concentration of the 

 sugar and of the alcohol, which is always present, by dilution with the added 

 boiled juice. The details given above show that neither of these influences 

 had any share in the effects observed by us. 



The Quantitative Estimation of Small Quantities of Nickel in 

 Organic Substances. 

 By H. W. Armit and A. Harden, D.Sc, Ph.D. 



(Communicated by Dr. C. J. Martin, F.R.S. Received December 5, 1905, — 

 Read February 1, 1906.) 



(From the Chemical Department of the Lister Institute of Preventive Medicine.) 



In the course of an investigation into the toxic action of certain nickel 

 compounds, it was found necessary to devise a method of detecting and 

 estimating nickel, when included in animal tissue, in quantities not exceeding 

 a few milligrammes per cent. 



A method has therefore been worked out, which, although in many respects 

 only differing from the usual methods in virtue of slight alterations of 

 detail, is capable of demonstrating extremely small quantities of nickel 

 accurately. The method may be divided into three stages : (1) The Ashing ; 

 (2) The Separating ; and (3) The Estimating stages. 



1. Ashing. — The substance to be examined must be placed in a porcelain 

 crucible (platinum is unsuitable, as a considerable loss of nickel takes place, 

 probably by an alloy of platinum and nickel being formed) and evaporated 

 to dryness over a water bath. If the substance be solid, it should be cut up 

 into small pieces. The crucible is then heated carefully with a Bunsen flame, 

 but it may be wise to further dry in a hot air oven or on a sand bath before 

 this. Then it is burned over a Fletcher burner, and lastly fully incinerated 

 in the blow-pipe flame. With some care, it is possible, as a rule, to oxidise 

 fully all the carbon, without recourse to any foreign material. The crucible 

 is then placed on the water bath, and 10 c.c. of pure hydrochloric acid are 

 added and allowed to evaporate to dryness, this process being repeated. 

 The residue is then extracted with water to which a small quantity of hydro- 



