﻿ORGANIC MATTER IN AIR. 9 



The dust-form of organic matter is determined by transferring the 

 asbestos or glass-wool absorbent to a clean casserole, adding 100 c. c. 

 of twice distilled water, .6 to 8 c. c. of permanganate solution, and 5 

 c. c. of 25 per cent, sulphuric acid, and then boiling for five minutes 

 and titrating with oxalic acid solution in the usual manner. In each 

 determination it is necessary to deduct the amount of oxygen con- 

 sumed by the 100 c. c. of water from the end-result. The results 

 obtained for the gaseous and dust-form of organic matter in air by this 

 method are given in Table III ; the form of apparatus employed is 

 shown in Fig. 2. 



Method III. 



A. Total oxidizable matter. This method is a modification of 

 that employed by Remsen. The air is aspirated through freshly 

 ignited and finely granular pumice-stone contained in a glass absorp- 

 tion tube, 18 c. m. in length and 1 c. m. in diameter. The pumice- 

 stone is then washed into a clean casserole with 100 c. c. of twice 

 distilled water, and the oxidizable matter determined in the usual 

 manner. From the results so obtained it is necessary to deduct the 

 amount of oxygen consumed by the 100 c. c. of water, and by a simi- 

 lar amount of the pumice-stone before it is exposed to the air. In 

 some of the experiments a dust-filter of freshly ignited asbestos was 

 prefixed to the absorption apparatus to exclude all dust. The results 

 obtained by this method are given in Table YI ; the apparatus em- 

 ployed in this method is shown in Fig. 8. 



B. Free and albuminoid ammonia. Remsen' s method. By this 

 method the free and albuminoid ammonia are determined by transfer- 

 ring the finely granular pumice-stone, through which a known volume 

 of ail' has been aspirated, to a clean retort with 500 c. c. of twice dis- 

 tilled water. Before beginning the aspiration of air the pumice-stone 

 is moistened with some twice distilled water. From the results ob- 

 tained in each determination it is necessary to deduct the amount of 

 ammonia given off by the same amount of water, as well as by the 

 same amount of the pumice-stone. The results obtained by this 

 method are shown in Tables IV and Y ; the apparatus employed is 

 shown in Fig. 3. 



Method IY. 



A. Carnelley and Mackie's method. In this method the air con- 

 tained in a four- to six-litre flask is agitated with 50 c. c. of yirW solu- 

 tion of permanganate of potash for about five minutes. Then 25 c. c. 

 of the permanganate solution are placed into a flat-bottomed glass 

 cylinder of such size that it is filled to within about 5 c. m. of the top 



