206 Pennington — A Chemico-Physiological 



The weighing bottle, for additional protection, was kept in 

 a sulphuric acid desiccator. 



The combustions were made in an open tube in a cur- 

 rent, first of air, then of oxygen, because the substance 

 proved exceedingly hard to burn. A period of eight hours 

 was required and the highest temperature available in the 

 combustion furnace. Very hard glass tubing was used. 

 This difficulty in burning is noteworthy, since it is rather 

 opposed to preconceived ideas. 



A white sublimate was invariably found in the front part 

 of the tube at the close of the operation. This proved to 

 be volatilized alkaline chlorides. The ash remaining in 

 the boat was light gray, but could not be weighed because 

 the loss of alkali introduced an error. 



The heating should be very gradual at first, so as to drive 

 over the water slowly but steadily. When this has been 

 collected in the calcium chloride tube the heat is increased 

 and maintained until all the carbon has been burnt to oxide. 



The oxygen in the potash bulb and calcium chloride 

 tube was displaced by a carefully purified air current and 

 the weighings made in this gas. Seven analyses of the 

 material yielded the following results : 



Maximum Minimum Mean 



Substance taken . . . 0.2398 0.0931 0.1S10 



Carbon found . . . .46.66% 46.15% 46.35% 



Hydrogen found . . 5- 6 9% 5-°°5% 5-43% 



Accepting for nitrogen 2.61 per cent., as was found by 

 a Kjeldahl determination, and for the percentage of ash in 

 the dry substance 15.43, the oxygen by difference is shown 

 to be 30.21 per cent. The primary composition of Spiro- 

 gyra nitida may then be formulated as 



Carbon 4 6 -35 



Hydrogen 5-43 



Nitrogen 2<61 



Oxygen 3°- 21 



Ash • J S-40 



100.00 



