TRANSACTIONS OF SECTION B. 



725 



10. 



On the Action of Permanganate of Potassium on Sodium Thiosulphate 

 and Sulphate. By G. E. Brown and Dr. W. W. J. Nicol. 



11. On the Application of Sodium Peroxide to Water Analysis. 

 By Dr. S. Kideal and A. J. Boult. 



No-w that sodium peroxide can be obtained commercially, its use in analysis 

 seems desirable. W. Hempel ^ has already shown that it is a useful oxidising 

 agent for the detection of chromium and manganese, and that it forms a very con- 

 venient reagent for opening up tungsten minerals and for effecting the decomposi- 

 tion of titanic iron ores. Since the commercial sodium peroxide is free from 

 sulphur, it can also be used quantitatively for estimating the sulphur in sulphides. 

 It occurred to us that an alkaline oxidising agent of this character, if used as a 

 substitute for alkaline permanganate in -water analysis, might throw some light 

 upon the character of the organic nitrogen in waters. Hitherto either methods for 

 determining the total nitrogen — e.g., Frankland's and Kjeldahl's, or Wanklyn's 

 well-known process in which only a portion of the nitrogen present in the organic 

 matter is discovered — have been employed. In this latter process very difierent 

 quantities of ammonia are obtained from the difierent classes of nitrogenous organic 

 bodies. Only when the nitrogen is present as some simple amido- compound like 

 urea, aspartic acid, or leucine does this process yield the whole of the nitrogen 

 present. Preusse and Tiemann - have shown in their review of the various pro- 

 cesses for determining organic substances in water that no reliance can be placed 

 upon this process for estimating the absolute quantity of nitrogen in many sub- 

 stances, and that, therefore, when used as a method of water analysis the quantities 

 of ammonia obtained are only relatively true for waters of the same type. A 

 comparison of the quantities of ammonia evolved from a water when treated with 

 alkaline permanganate and with sodium peroxide might therefore possibly afford 

 a means of differentiating the nitrogenous constituents. With this purpose in view 

 we have compared in the ordinary course of analysis the amounts of ammonia 

 given off under these two ti-eatments. In one case when using one grm. of 

 sodium peroxide per half litre of water, the total ammonia evolved was equal to 

 0-027 part per 100,000, while with alkaline permanganate 0-050 part per 100,000 

 was obtained. On repeating this experiment with the same water and under 

 similar conditions, 0-026 part per 100,000 was yielded by the peroxide and 0048 

 by the permanganate. The addition of a further quantity of the sodium peroxide 

 and further distilling did not increase the quantity of ammonia produced, and it 

 was therefore evident that the sodium peroxide had failed to break down the 

 organic nitrogenous substances present to the same extent as had the alkaline 

 permanganate. In fact, we have since found it possible to obtain a fresh quantity 

 of ammonia from a water after treatment with sodium peroxide by the addition of 

 the alkaline permanganate. The following table gives the results obtained in 

 parts per 100,000 with four samples of water : — 



From these figures it will be seen that the sodium peroxide in no case oxidises 

 the organic matter present to the same extent as does the permanganate. The 

 peroxide seems to liberate a portion of the nitrogen which is included in that set 

 free by the alkaline permanganate, as the total ammonia obtained by the action of 



k 



' Zeit. anorg. Chem., 3, 193. 



= Berichte, 12, laOS. 



