PROFESSOR H. B. DIXON AND MR. E. C. EDGAR 



BECK for the identification of pure phosphorus pentoxide : (l) it did not reduce a 

 10-per cent, solution of silver nitrate; (2) it did not reduce mercuric chloride when 

 boiled with it ; and (3) on evaporating an aqueous solution of it to dryness and 

 igniting moderately, no odour of phosphine was detected. 



Palladium Foil. The palladium, which was used in the form of thin foil cut into 

 very small pieces, was heated to dull redness in a current of pure dry air for twenty- 

 four hours, in order to eliminate any grease which might have been acquired during 

 rolling. It was then heated in glazed porcelain tubes to a bright heat, in vacua, for 

 six hours. 



Sodium Thiosulphate. The sodium thiosulphate used was re-crystallised from 

 water four times and was dried, in vacuo, over calcium chloride ; it was pure white in 

 colour and its solution was neutral to litmus. 



Sodium Hydrogen Carbonate. The sodium hydrogen carbonate used for the 

 preparation of carbonic acid, in an atmosphere of which the titration of the iodine 

 contained in the combustion bulb was carried out, was purified by exposing the solid, 

 at 70 C., to the action of a slow stream of carbonic acid gas passing through it. The 

 carbonic acid was prepared by the action of hydrochloric acid on marble, and, before 

 reaching the carbonate, was washed thoroughly with water. When the current of 

 gas had been passing for three hours, the carbonate was allowed to cool in it until 

 the ordinary temperature had been reached. Sodium hydrogen carbonate so prepared 

 had no effect in impairing the accuracy of titrations of thiosulphate by means of the 

 standard solution of iodine in potassium iodide. The gas obtained on heating the 

 acid carbonate was completely absorbed by potassium hydrate. 



Starch Solution. The solution of starch, used as an indicator, was prepared by 

 adding soluble starch, in very small quantities at a time, to boiling water which had 

 been purified. When the solution commenced to assume a faint opalescent blue, the 

 addition was discontinued. The solution, on cooling, was preserved in a tightly 

 stoppered bottle, and to prevent any fermentation, a little mercuric iodide was added 

 and dispersed through the solution by vigorous shaking. 



Platinised Pumice. Pumice stone was ground into small fragments and sifted 

 through two sieves the first of 2 sq. millims. mesh, the second 1 sq. millim. ; the 

 part remaining on the second was transferred to a porcelain basin and washed 

 thoroughly with aqua regia. After decanting the supernatant acid, the mass was 

 washed with water until the washings were no longer acid. It was then dried in a 

 porcelain crucible contained in an air-bath at 120 C. The dried product was 

 saturated with a concentrated solution of platinic chloride, excess of ammonium 

 hydrate added, and the mass stirred until the yellow colour of the platinic chloride 

 had disappeared from the supernatant liquid, which was then decanted and the 

 platinised pumice carefully dried. It was then heated in a deep porcelain crucible 

 until fumes were no longer evolved. A lid was placed on the crucible and the whole 

 heated to a dull red heat for twelve hours. On cooling, the platinised pumice was 



