﻿ORGANIC MATTER IN AIR. 1^ 



small proportion of it is "asnallj present in the gaseous form, the 

 method of analysis which will be most likely to present results that 

 possess any degree of accuracy will be the one which abstracts the dust 

 particles most efficiently from the sample of air analyzed. In the 

 second place, the most reliable method will be the one in which the 

 organic matter is converted into ammonia with the least possibility 

 of any considerable experimental error arising from the manipulation. 

 The method which has seemed to me to meet all these indications 

 most satisfactorily is that of Kemsen. Here the absorbent material 

 consists of finely granular pumice-stone that has been freshly ignited 

 for twelve to twenty-four hours. This is filled into a small glass ab- 

 sorption tube, twenty centimetres in length, consisting of a narrow 

 portion four centimetres long and three millimetres in internal diameter, 

 and of a wider portion sixteen centimetres long and twelve millimetres 

 in internal diameter. The mouth of this tube is closed by means of per- 

 forated rubber cork bearing a short piece of glass tubing through which 

 the air enters. This tube is cleansed by placing it for some hours in a 

 mixture of bichromate of potash, sulphuric acid, and water. It is thor- 

 oughly rinsed with twice distilled water, until free of all trace of the 

 cleansing mixture, and wiped on the outside with a clean towel. It is. 

 now ready to be filled with the freshly ignited pumice-stone. This is. 

 transferred from the plantinum crucible with a clean, porcelain, spoon- 

 shaped spatula. As soon as the pumice has cooled somewhat it is well 

 moistened with twice distilled water, the rubber stopper is put in place, 

 and the narrow portion attached to a gas-meter or aspirator by means 

 of rubber tubing. The moistened granular pumice-stone thus affords, 

 an excellent absorbent for the dust particles in the air aspirated 

 through it. 



None of the absorbents used in the other methods seem to afford 

 such favorable opportunities for the abstraction of the dust particles in 

 the air. This is especially the case with liquid absorbent materials. The 

 air passes through these in the form of fine bubbles, but under such cir- 

 cumstances the dust particles may also pass with these air bubbles, be- 

 cause they are moistened with considerable difficulty. Neither can the 

 absorbent materials used in the other methods be subjected to such 

 purifying processes as the piimice-stone, which can be heated to red- 

 ness without injuring its absorbent powers. 



Those methods in which the organic matter is determined by estimat- 

 ing the quantity of permanganate reduced by it seem to be less satis- 

 factory in many respects than those in which the organic matter is 

 converted into ammonia. In the first place, such results are always in- 

 fluenced by the reducing action of other bodies in the air besides those 

 of organic nature. In the second place the rate at which many organic 



