January 4, 1918] 



SCIENCE 



25 



sible to avoid such defects entirely, but it is 

 interesting to note that no beaker has proved 

 •defective after very long and severe use. 



The place subjected to greatest danger of 

 puncture and that which allows greatest leak- 

 age is where the exposed surfaces of the solu- 

 tion inside and out come in contact with the 

 surface of the beakers. This defect can be re- 

 duced considerably by filling the beakers with 

 the salt solution to a slightly different level 

 from that of their containers. Care should be 

 taken not to wet the portion of the beaker that 

 is not immersed. To eliminate sparking quite 

 completely, however, the surfaces of the so- 

 lution inside the beakers and that surround- 

 ing the beakers were covered with a layer of 

 oil 5 cm. deep. For this purpose a 300-degree 

 mineral seal oil was used. This oil, as Mr. C. 

 E. Skinner kindly informed us, has very 

 good dialectric properties — as good as can be 

 expected from an oil not free from water. 

 Whether this layer of oil eliminated sparking 

 at the sacrifice of some capacity we have not 

 determined. 



The capacity of these condensers was esti- 

 mated by the method of divided discharge and 

 by the method of mixtures. The capacity of 

 each of the five jars containing four beakers 

 each was: .0088 M.F., .0091 M.F., .0093 M.F., 

 .010 M.F., .0088 M.F. respectively. The mean 

 of these capacities is .0092 M.F. A similar 

 estimation of the capacity of two such beakers 

 covered with tinfoil indicated that their com- 

 bined capacity was very appreciably less than 

 two beakers of the wet condenser. This is 

 probably due to the unevenness of the surface 

 and the difficulty of making contact between 

 the glass and the tinfoil. 



A comparison was made between the wet 

 condenser as above described in which beak- 

 ers of Jena glass and of " Pyrex " glass were 

 used. The dimensions of these beakers were 

 approximately the same. Assuming that the 

 average thickness of the " Pyrex " beaker is 

 equal to that of the Jena and assuming the 

 dielectric constant of Jena glass to be 6.5, that 

 of " Pyrex " glass must be about 4.3. 



A comparison was also made as to the influ- 

 ence of the character of the conducting 



medium. Beaker condensers were set up 

 using mercury, concentrated salt solution and 

 distilled water (iron still), respectively. The 

 capacities of the latter two were equal within 

 the limits of error of measurements, while the 

 capacity when using mercury was 10 per cent, 

 higher than when using the salt solution. 

 The slight superiority of mercury at low con- 

 stant potential seems to be very greatly en- 

 hanced at the high and discontinuous poten- 

 tials employed to produce the spark, where, 

 judging by the fatness of the spark, the ca- 

 pacity of the condenser with mercury is three 

 or four times as great as that of the condenser 

 with salt solution. 



This wet condenser has given perfect satis- 

 faction under severe use for many months. 

 Its cost is approximately the same as the glass 

 plate condenser and considerably less than 

 similar condensers covered with tinfoil. 



E. Karrer, 

 H. S. Newcomer 

 The Physical Laboratory op the 



United Gas Improvement Company, 

 The Laboratory op the Henry Phipps 

 Institute of the University op 

 Pennsylvania 



Philadelphia, Pa. 



BOSTON MEETING OF THE AMERICAN 

 CHEMICAL SOCIETY. VI 



DIVISION OP INDUSTRL\L CHEMISTS AND CHEMICAL 

 ENGINEERS 



H. E. Howe, Chairman. 

 S. H. Salisbury, Jr., Secretary. 

 Conference on ' ' The Industrial Chemist in War 

 Time" 

 The craclcing of solvent naphtha in the presence 

 of Blau gas: Gustav Eqlopf. Solvent naphtha 

 derived from the thermal decomposition of coal 

 was passed through a carburetted water gas set in 

 the presence of Blau gas at a temperature of 850° 

 C. to produce toluene. The solvent naphtha used 

 gave a distillation range of 93 per cent, between 

 130° C. and 165° C. First drop at 128° C. and 

 dry at 183° C. Distillation determined by means 

 of a 100 c.c. Standard Engler flask. The percent- 

 age yield of toluene in the recovered oil was nine- 

 teen, and upon the basis of solvent naphtha used 

 eleven and one half per cent. 



