140 



NEW RESEARCHES ON LIQUID AIR. 



with its 0.1 per cent of argon, behaved in substantially the same way 

 on liquefaction. 



Liquid nitric oxide. — Great interest attaches to the behavior of nitric 

 oxide at low temperatures. Professor Olszewski has examined the 

 liquid and describes it as colorless. Samples of nitric oxide have been 

 prepared in different ways. These have been transferred to liquefac 

 tion flasks, where they were left in contact with anhydrous potash, sul- 

 phuric acid alone, a mixture of sulphate of aniline and sulphuric acid, 

 or phosphoric acid, for many days before use. Each of the samples, 

 when cooled, gave a nearly white solid, melting into a blue liquid. The 

 color is more marked at the melting point than at the boiling point. 

 Liquid nitric oxide is not magnetic; neither is the solid phosphorescent. 

 Color in the oxides of nitrogen evidently begins with the second oxide.. 

 Solid nitric oxide does not show any chemical action when placed in 

 contact with liquid oxygen, provided the tube containing it is completely 

 immersed; but if the tube full of liquid oxygen is lifted into the air, 

 almost instantly a violent explosion takes place. 



Specific gravities taken in liquid oxygen. — In a good vacuum vessel 

 specific gravities may be taken in liquid oxygen with as great ease as 

 in water. The shape of the vacuum vessel which works best is shown 

 in fig. 1, Plate V. It must contain excess of mercury and be thoroughly 

 boiled out, so that the inner vessel becomes completely coated with a 

 mercury mirror as soon as the liquid oxygen is filled in. Instead of a 

 mercury vacuum, the interior maybe silvered and highly exhausted by a 

 Sprengle pump. The flasks must also be thoroughly clean and free 

 from dust, otherwise the liquid oxygen will not remain tranquil. Any 

 superheating is prevented by inserting a long narrow piece of wood for 

 a moment before the final weighing. 



Some twenty substances were weighed in liquid oxygen, 1 and the 

 apparent relative density of the oxygen determined. The results were 

 then corrected, using Pizeau's values for the variation of the coefficient 

 of expansion of the solids employed, and thereby the real density of 

 liquid oxygen calculated. The resulting value was 1.1375, bar. 766.5, 

 in the case of such different substances as cadmium, silver, lead, cop- 

 per, silver iodide, calc-spar, rock crystal. The following table gives 

 some of the observations: 



Mean cubical coeficient of 



expansion between 



15° 0.-183° C. 



Apparent 

 density of liq- 

 uid oxygen. 



Heal density 

 of liquid 

 oxygen. 



Cadmium, 7986 X 10" 6 



Lead, 7892 X 10 " 6 



Copper, 4266 X 10 E 



Silver, 5185X10-" 



Calc-spar, 1123 X 10 6 



Rock crystal, 2769 X 10 - 5 



Silver iodide, 0189 X 10 - 5 



1. 1188 

 1. 1197 

 1.1278 

 1. 1278 

 1. 1352 

 1. 1316 

 1. 1372 



1. 1359 

 1. 1367 

 1. 1370 

 1. 1385 

 1. 1376 

 1. 1376 

 1. 1376 



The liquid oxygen might possibly contain a small proportion of nitrogen. 



