Chemistry and Physics. 385 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On New Methods for Measuring Gases. — Several methods 

 for measuring gases have been described by Blair, which seem to 

 present important advantages. In the first, which is a new com- 

 pensation method, it is the gas under examination, and not the 

 standard gas with which it is to be compared, which is kept at 

 constant volume or is adjusted to a known fraction of the original 

 volume. In the apparatus used for air analysis, the whole is sur- 

 rounded with a water jacket. It consists of two tubes A and B; 

 A being filled with the gas to be tested and B with the standard 

 volume. The tube B has a cylindrical bulb at its top of a 

 capacity of 100 cc , the tube itself below this holding l cc and being 

 graduated to 0*0 l cc . The parallel tube A has a 79*5 CC cylindrical 

 bulb at its top and just below it a second bulb of 20*5 CC . After 

 filling both tubes to the 100 cc mark at the atmospheric pressure, 

 their upper ends are connected by means of taps with a re-curved 

 capillary tube having a drop of liquid in the bend. Since the 

 pressure is the same in the two tubes, the drop will remain in the 

 center when the taps are opened. The carbon dioxide is then 

 absorbed, the liquid is brought to its original level in the two 

 tubes and the taps are opened. Since the absorption has slightly 

 decreased the pressure in A, the drop moves to that side. The 

 liquid in B is then lowered by lowering the reservoir connected to 

 the ends of both tubes by a rubber hose, until the drop comes 

 back to the center. If to do this the level of the liquid in B has 

 been lowered 0'15 cc , the percentage of C0 2 is 0*15 X (100/ 100*15) 

 Next the oxygen is absorbed and the process is repeated, except 

 that the liquid in A is brought to the upper level between the 

 two bulbs in place of the lower level. If the final level is 0*53" the 

 percentage of oxygen is 20*5 + 0-53 X (79*5 / 100*53). In this way 

 very great accuracy is secured, all the measurements being made 

 under nearly the same pressure, though each special gas requires 

 specially divided tubes. Evidently this same apparatus can be 

 used with the ordinary compensation method by placing the gas 

 to be examined in B, which it completely fills; the standard gas 

 volume being contained in A. Indeed a combination of the two 

 may be employed using the second method first and then the first 

 method. In a second method the measurements of volume are 

 made by means of pressure readings. A pipette consisting of 

 five bulbs is made use of, inclosed in a water jacket. Each bulb 

 has an approximate capacity of 20 cc and on the connecting tubes 

 between each pair of bulbs a mark is made, the volume of the 

 pipette down to each mark being accurately known. Besides this 

 pipette a graduated manometer tube is provided, connected with 

 a movable reservoir, which tube is clamped in position and reaches 

 to about 60 cm above and below the lowest mark of the pipette ; 



