,41) DR CHARLES HUNTER STEWART ON THE ESTIMATION OF 



settle. In titrating this solution, 10 c.c. is used. This apparatus seems to the writer 

 inefficient for getting accurate results. 



First. — As to the method of closing the flask in which the combustion is carried 

 on. Okada is aware of this, and points out that, considering the high pressure in the 

 inside of the flask, it is necessary to see that the ground glass tube fits tightly. But 

 "if this and the other connections are not tight the smell of sulphurous acid will make 

 it apparent." Any apparatus the accuracy of which requires such a proof cannot be 

 considered sufficient. 



Second. — Considering the large quantity of carbonic acid (in some of his experiments 

 250 c.c.) produced, and the consequently larger amount of sulphurous acid that must be 

 produced at the same time, his means of absorption of both gases are insufficient. In 

 the writer's experience, two carbonic acid and two sulphurous acid tubes are necessary 

 in such an apparatus to ensure complete absorption of these gases, however strong the 

 respective solutions may be. 



Third. — There is no sweeping out of the apparatus before the experiment and no 

 sweeping out of the combustion flask after the experiment. In the first case there 

 must be a gain, in the second a loss, of carbonic acid. 



In 1892 the author communicated to the Royal Society of Edinburgh a paper 

 containing a description of an apparatus which he had devised for this purpose, as well 

 as the results he had obtained by its use. Fig. 2 shows the apparatus. (A) is a 

 long-necked bohemian glass flask of about 300 c.c. capacity, fitted with a rubber cork 

 having two holes bored through it. Through one hole passes a tube (the inlet tube) 

 to within 2 inches from the bottom of the flask. The end of the tube in the flask is 

 slightly bent down and slightly contracted. The part of the tube outside the flask 

 has a bulb blown on it which is closed at its outer end by a rubber tube and clip (B). 

 This tube is connected by rubber tubing and a T-tube with the series of bulbs and 

 tubes at (C). Through the other hole in the cork passes another tube (the outlet tube), 

 projecting about ^ inch into the flask, and connected at its outer end by means of a 

 T-tube with both the tubes and bulbs at (C) and the absorption flasks and tubes at (D). 

 (Dj) is empty, (D 2 ) and (D ;s ) are half filled with a boiled and acidified saturated solution 

 of permanganate of potassium for the purpose of absorbing the sulphurous acid produced 

 in the reaction. (D 4 ) is one-half filled with a solution of barium nitrate and silver 

 nitrate in order to catch any trace of sulphuric acid or hydrochloric acid which might 

 accidentally pass over. (D 5 ) is empty and is connected by rubber tubing with two 

 tubes (E) containing baryta solution for absorbing the carbonic acid produced in the 

 reaction, and the second of these is connected by rubber tubing with a water-pump. 

 (C,) contains strong sulphuric acid, (C 2 ) and (C 3 ) have their left limbs filled with 

 soda lime and their right limbs with fused chloride of calcium. (C 4 ) contains a 

 strong solution of caustic soda. The tubes (E) are a modification of Petten- 

 kofer's tube. Fig. 3 (A) shows the ordinary Pettenkofer tube. Fig. 3 (B) 





