Chemistry and Physics. 153 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. Apparatus for Determining the Density of Liquids. — A 

 very simple means for taking the specific gravity of liquids has 

 been devised by F. Girardet. It consists of two perpendicular 

 glass tubes, resembling barometer-tubes, which are open at the 

 bottom, and are connected at the top so that suction can be 

 applied to both tubes at once by means of a rubber tube. Each 

 tube has behind it a paper millimeter scale extending from an 

 arbitrary zero point a few centimeters above its bottom to 500 mm 

 or more, near the top. To take the specific gravity of a liquid, 

 the latter is placed in a small, cylindrical, glass vessel so that 

 one of the upright tubes dips into it, while distilled water is 

 placed at the mouth of the other tube and in a dish of the same 

 size. Suction is now applied until the liquid to be tested remains, 

 when a screw-clamp on the rubber tube is closed, at a convenient 

 point high up in the tube, say 500 mm , and the height of the water 

 is also read. Then air is admitted until the columns have fallen 

 to points near the bottoms of the scales, for example, until the 

 liquid to be tested is at zero, when the positions of the two col- 

 umns are again recorded. It is evident that the columns thus 

 measured are inversely as the specific gravities of the liquids ; 

 hence, since one of them is water, it is only necessary to divide 

 the fall of the water column by that of the other liquid in order 

 to obtain the specific gravity of the latter. The effect of capil- 

 larity is eliminated by the two readings if the tubes are of uni- 

 form caliber. In the apparatus described the tubes were of about 

 8 mm exterior diameter, so that the quantity of liquid needed was 

 very small. Determinations were made with various liquids, and 

 results were obtained which agreed closely with those obtained 

 by a Mohr's balance. Slight errors were encountered when vola- 

 tile liquids were used, but satisfactory results were obtained with 

 ethyl alcohol and with ammonia of *985 specific gravity. The 

 apparatus is easily constructed at slight expense ; it is much more 

 accurate than ordinary specific gravity spindles, and it may be 

 used to replace a series of these, as it is applicable to liquids 

 which are heavier or lighter than water. Where readings are 

 made to ^ mm , with columns of about 400 mm , the probable error is 

 calculated to be ^Vc of the absolute value. The time required 

 for the determination is only about one minute. — Bulletin, xxv, 

 936. h. l. w. 



2. The supposed Existence of an Oxide of Hydrogen higher 

 than the Dioxide. — The possible existence of an oxide of hydro- 

 gen higher than H 2 2 was suggested by Bach a year or two ago, 

 on the ground that when hydrogen peroxide is acidified with sul- 

 phuric acid the amount of oxygen evolved by potassium perman- 

 ganate is greater that the amount calculated from the permanga- 

 nate used. Ramsay has now confirmed the fact just stated, but 



