Substances in the Wet Way. 373 



iodine in the boiling ; the long tube of the bottle was used as 

 an inlet tube and was closed externally by a rubber cap during 

 the boiling. After cooling, the excess of iodine used was 

 determined by titration with decinormal arsenious acid solu- 

 tion and the iodine lost calculated on barium hydroxide mole- 

 cule for molecule. 



Potassium permanganate was prepared for use by dissolving 

 the commercial salt in water, and boiling this solution, made 

 acid with sulphuric acid, until free from carbon dioxide. Water 

 was also prepared free from carbon dioxide by boiling distilled 

 water until one-third had been driven off in steam and was 

 kept until used in full-stoppered flasks. 



For the first determinations of carbon, crystallized ammonium 

 oxalate was weighed out and introduced into the boiling flask 

 with 10-15 cm3 of pure water and the flasks connected as dis- 

 cribed above with an appropriate amount of barium hydroxide 

 solution (3-5 cm3 in excess of the amount required to precipitate 

 the carbon dioxide to be determined) in the absorption flask. 

 The whole system was then evacuated with the water pump to 

 a pressure of 200-225 mm and the oxalate solution in the boil- 

 ing flask warmed. An excess of potassium permanganate solu- 

 tion was then run in through the funnel tube and the mixture 

 warmed again, when the oxidation of the oxalate was shown 

 by the carbon dioxide evolved. The carbon dioxide was com- 

 pletely set free by the introduction of 10 cm3 of sulphuric acid 

 (1 : 4) and was driven completely to the absorption flask by 

 boiling for five minutes. During the passage of the gas into 

 the absorption flask, it was shaken frequently and was kept 

 cool by standing in a dish of water and by pouring cold water 

 over it from time to time. If, during the boiling, any fears 

 are entertained as to the strength of the vacuum in the flasks, 

 they may be easily allayed by opening momentarily the stop 

 cock of the funnel tube and noting the direction of the flow 

 of water, contained in the funnel. After the boiling was 

 ended, the atmospheric pressure was restored by allowing air, 

 purified from carbon dioxide by passage through potash bulbs, 

 to enter through the funnel tube of the boiling flask. Then 

 the flasks were disconnected and the stopper of the absorption 

 flask with its attachments was removed, the valve and its tube 

 being carefully washed free from barium hydroxide. A sec- 

 ond stopper, which was provided with a separating funnel, and a 

 Will and Yarrentrapp absorption apparatus, containing water to 

 serve as a trap, was inserted into the mouth of the absorption 

 flask and the emulsion brought to the boiling point. Deci- 

 normal iodine solution was then run in through the funnel 

 tube in sufficient quantity to destroy the larger part of the 

 excess of barium hydroxide and the emulsion brought to the 



