Chemistry and Physics. 149 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Gravi-volumeter. — An instrument by means of which 

 the mass of a given gas is given directly from a single reading of 

 its volume, has been devised by Japp, who has called it a gravi- 

 volumeter. It is a modification of the gas volumeter of Lunge. 

 The apparatus consists of two gas burettes, each of 50 oc capac- 

 ity, provided with obliquely bored taps. One of these, A, has a 

 three-way tap, and is used as the gas measuring tube; the other, 

 B, has only a single tap and serves as the regulator tube. Both 

 tubes are moistened internally, in order to saturate the gases they 

 contain with aqueous vapor, and both are connected by means of 

 stout flexible tubing and a T piece with the same movable reser- 

 voir of* mercury. In calculating the "gravi-volumetric values" 

 of the different gases to be measured, the 25 cc division of the 

 regulator tube is taken as the starting point. In the case of 

 nitrogen, for example, the volume to which 25 cc of standard- 

 dry nitrogen must be brought in order that l cc may correspond 

 with one milligram of the gas, is calculated. Since the mass of 

 25 oe of nitrogen is 0-001256 X 25 = 0-0314 gram, or 31*4 milli- 

 grams, this mass must be brought to 31-4°°. The division 31*4 

 on the regulator tube is therefore marked N 2 . Similar points are 

 determined for other gases and marked 2 , C0 2 , etc. The 

 barometer and thermometer are now read, the volume which 25 co 

 of standard-dry air would occupy at this pressure and tem- 

 perature is calculated, and this volume of air is admitted into the 

 regulator tube. Suppose it is desired to ascertain the mass of a 

 quantity of nitrogen contained in the measuring tube. It is nec- 

 essary only to raise or lower the mercury reservoir until the mer- 

 cury in the regulator tube stands at the nitrogen mark, 31-4, this 

 regulator tube being adjusted so that the mercury level in it and 

 in ti e measuring tube is the same. Under these conditions each 

 cubic centimeter of nitrogen in the measuring tube has the mass 

 of one milligram; so that the reading of the gas volume in cubic 

 centimeters and tenths gives at once the mass of the gas in milli- 

 grams and tenths. By bringing the mercury in the regulator 

 tube to the proper level, the mass of any other gas may be read 

 in a similar manner. If it be brought to the 25 mark, the gas or 

 mixture of gases will have the volume it would occupy in the 

 standard-dry state and the apparatus acts as a gas-volumeter. — 

 J. Chem. jSoc, lix, 894, November, 1891. g. f. b. 



2. On the Element Fluorine. — An extended memoir upon the 

 element fluorine has been published by Moissan", giving the re- 

 sults of his more recent researches upon this substance. An 

 excellent resume of this paper has been given in English by 

 Tutton. For preparing the fluorine the platinum U-tube em- 

 ployed in the later experiments was much larger and had a 



Am. Jour. Sci. — Third Series, Vol. XLIII, No. 254.— February, 1892. 

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