﻿ORGANIC MATTER IN AIR. 



permanganate of potash of known strength, are shaken with the air in 

 a flask of known capacity. The flask is refilled with air and again 

 shaken — " air washing," — and this process is continued until all the per- 

 manganate is decolorized. The volume of air required to decolorize 

 the permanganate will indicate the quantity of organic matter contained 

 in it. 



Uffelmann" determines the quantity of organic matter in air by 

 means of a solution of permanganate of potash, of which 1 c. c. equals 

 0.395 mg. of KMnO^, or 0.1 mg. of oxygen, and requires 0.7875 mg. of 

 oxalic acid to neutralize it. The permanganate solution is placed in a 

 small flask, the stopper of which carries two glass tubes. One of these 

 tubes is of sufficient size to serve as a dust-filter and contains freshly 

 ignited asbestos or glass-wool ; the other tube serves to connect the appa- 

 ratus with a small aspirator, about one litre in capacity. The apparatus is 

 cleansed with hot permanganate solution. One cubic centimetre of the 

 permanganate solution is then placed in the flask with 9 c. c. of pure 

 distilled water, and acidulated with several drops of dilute hydrochloric 

 acid. Ten to twenty litres of air are aspirated through the apparatus. 

 The asbestos or glass-wool absorbent is transferred to a clean casserole 

 with 60 c. c. of distilled water ; 2 c. c. of KMnO^ solution and 1 c. c. of 

 dilute sulphuric acid are added and boiled for five minutes. The un- 

 reduced permanganate remaining in solution is then titrated with oxalic 

 acid solution. The permanganate solution in the flask is treated in the 

 same manner. The two results will show the quantity of gaseous 

 and of dust-form of organic matter in the air aspirated through the 

 apparatus. 



A second method devised by Ufielmann is as follows : Two flat- 

 bottomed test-tubes, each closed with a double-bored rubber stopper, 

 are attached to each other. A dust-filter of asbestos or of glass-wool 

 is attached to the entrance-tube of the first test-tube. The first of these 

 test-tubes contains a. dilute solution of caustic potash and the second 

 a dilute solution of sulphuric acid ; each solution being of about 1 per 

 cent, strength. By means of a rubber syringe of 50 c. c. capacity, 10 

 to 20 litres of air are pumped throu.gh the apparatus. The two solu- 

 tions are then mixed and the amount of organic oxidizable matter 

 determined in the usual manner. 



Carnelley and Mackie ^^ employ a solution of permanganate of 

 potash of Y^^-Q strength, 1 c. c. of which equals 0.008 mg. of oxygen, 

 or 0.0000056 litres of oxygen at 0° C. and 760 mm. The solution is 

 usually kept of -^ strength and diluted as required ; about 50 c. c. of 

 dilute sulphuric acid (1 : 6) being added to each litre of the weak solu- 

 tion. For the collection of samples of air large, well-stoppered jars, of 

 about 8.5 litres capacity, are used. The jars are first rinsed with a 



