Phelps and Weed — Succinic Acid. 147 



ardized as the silver chloride, as well as the organic substances 

 mentioned above, is brought into comparison with decinormal 

 solutions of sodium thiosulphate and iodine, standardized 

 against a carefully prepared solution of arsenious oxide, it is 

 evident that the two standards, silver chloride and the organic 

 substances, are in agreement with the third standard, a deci- 

 normal arsenite solution made up with the precautions given 

 above. 



Further, it is evident that the incompleteness of the action 

 of mineral acid on a mixture of iodide and iodate in dilute 

 solution, as shown by Furry,*, does not take place appreciably 

 under the conditions used here with decinormal solutions. 

 This is particularly striking in view of the different procedures 

 used in the experiments recorded. When, however, the action 

 of centinormal solutions of iodine, thiosulphate, and hydro- 

 chloric acid w T as tested with the iodide-iodate mixture, the 

 phenomena observed by Furry became very apparent, compara- 

 tively wide variations in the results being obtained. 



That this method of standardization in alkalimetry could 

 also be used in the presence of carbonates is shown in Table 

 II. In the experiments included in that table, definite portions 

 of the decinormal solution of sodium hydroxide were first 

 drawn from the burette. Purified carbon dioxide was then 

 passed into this solution for different lengths of time, convert- 

 ing the sodium hydroxide to the carbonate or bicarbonate. 

 The solution of sulphuric acid w T as then added in excess, and 

 the carbon dioxide set free was completely driven out of the 

 solution by boiling in a flask, trapped with the bulb-end of an 

 ordinary calcium chloride tube, to prevent mechanical loss, the 

 boiling being continued until the volume was reduced one- 

 third. After cooling, the excess of acid was estimated in tw T o 

 ways. In experiments (1) to (4) inclusive, the excess of acid 

 was determined by direct titration, in presence of phenolph- 

 thalein as an indicator, with the decinormal solution of sodium 

 hydroxide. The second method of determining the excess of 

 the sulphuric acid was used in experiments (5) to (8) inclusive. 

 To these, after cooling, a solution, containing one gram of 

 potassium iodide and fifty cubic centimeters of the solution of 

 potassium iodate described above, was added, after the free 

 iodine had been removed from this iodide-iodate solution by 

 the addition of a dilute sodium thiosulphate solution in the 

 presence of starch as an indicator. Definite, portions of the 

 decinormal sodium thiosulphate solution were then added in 

 excess, and this excess was determined by titration with the 

 decinormal iodine solution. 



* Loc. cit. 



