MA TURR 



217 



THURSDAY, JANUARY 17, 1878 



THE DENSITY OF LIQUID OXYGEN 



THE magnificent experimental methods devised by 

 MM. Cailletet and Pictet have already begun to 

 increase the number of the " Constants of Nature." M. 

 Pictet, although in a neck-and-neck race he was beaten 

 by Cailletet in the liquefaction of hydrogen, has left his 

 competitor in the rear with regard to a result of the first 

 importance on the density of oxygen. The noble rivalry 

 between the Ecole Normale Supdrieure of Paris and the 

 Atelier de Physique of Geneva bids fair not only to con- 

 tinually increase in interest, but to become the central 

 feature in the progress of physical science for some time. 



A telegram from M. Pictet announcing that hydrogen 

 had been solidified was sent to M. Dumas on January 11. 

 The illustrious chemist read the telegram at a sitting of 

 the Socidtd d'Encouragement, of which he was the chair- 

 man, and which was holding its regular semi-monthly 

 meeting on that very evening. M. Dumas reminded his 

 hearers with his wonted force and propriety of expression, 

 that in the first edition of his " Traitd de Chimie," published 

 about forty years ago, he had called hydrogen a gaseous 

 metal. He said he had been led to hold this view by 

 seeing how small was the affinity of hydrogen for metals 

 and how great for metalloids. 



M. Dumas said moreover that his peculiar ideas had 

 received some degree of confirmation from the discovery 

 of the large conductibility of hydrogen for heat and elec- 

 tricity, but that the first real demonstration had been 

 given by MM. Cailletet and Pictet. It was for him a great 

 satisfaction having lived long enough to see that most 

 important fact established so clearly, " That you May feel 

 certain, gentlemen, that in drinking a glass of water you 

 arc certainly absorbing a inetallic oxide." 



M. Piciet, in the experiments, the results of which were 

 telegraphed to M. Dumas, as we have seen, prepared the 

 hydrogen by the decomposition of potassic formiate by 

 means of potassic [hydrate. This reaction, according to 

 Berthelot, gives the gas of the utmost purity. The 

 pressure was commenced at 8,30 P.M., it was increased 

 gradually, and in a little more than half an hour (at 9.7) 

 it reached 650 atmospheres. At this moment the pressure 

 remained stationary for some seconds, the stop-cock was 

 opened, and a jet of a steel blue colour escaped with 

 a strident noise, comparable to that heard when a bar 

 of iron is plunged into water. 



This jet suddenly became intermittent, and the 

 spectators observed a hail of solid corpuscles projected 

 with violence on the ground, where they produced a 

 crackling noise. The stop-cock was then again closed, 

 the manometer indicating 370 atmospheres. This slowly 

 descended to 320, at which point it remained stationary 

 for some minutes. Then it rose to 325. The stop-cock 

 was again opened, the jet was now so intermittent, that it 

 was believed that an actual crystallisation of hydrogen (!) 

 had gone on inside the tube. This was proved by the fact 

 that liquid hydrogen flowed out of the jet when the 

 temperature was increased by the stoppage of the pumps. 



M. Dumas, considering oxygen as belonging to the 

 Vol. xvii.— No. 429 



sulphur group, and isomorphOus bodies as having the 

 same atomic volume, z>., the quotient obtained when the 

 atomic weight is divided by the density, had concluded 

 that, the atomic volume of sulphur being ^^, that of 

 oxygen would be 'j", and reciprocally, that the density of 

 liquid or solid oxygen would be \%, that is the atomic 

 volume divided by the atomic weight = i, which is the 

 density of water. 



M, Dumas having communicated these considerations 

 to M. Pictet, has elicited a most interesting response from 

 him. He writes : — 



" You arrive at the expression of the density of liquid 

 oxygen as being represented by |§- = i = 8 in the solid 

 state, and probably the liquid one also, neglecting the 

 variation due to expansion. 



" I have the great satisfaction of being able to announce 

 to you the complete experimental demonstration of the 

 theoretical views enunciated by you now some time ago 

 at Geneva. This demonstration has been arrived at as 

 follows : — 



" I know directly and very exactly— 



" I. The exact volume of the interior of the wrought 

 iron shell and the volume of potassic chlorate decomposed 

 into oxygen and potassic chloride. 



"II. The temperature of the shell at the moment of 

 complete decomposition. 



"III. The volume of the tube in which the condensa- 

 tion of oxygen is brought about. 



" IV. The pressure before and after condensation. 



" V. The pressures indicated by the manometer after two 

 or three successive jets, till the moment the point of satu- 

 ration is reached, and after which the gas issues in a 

 gaseous form. 



" These various data, combined with the gaseous density 

 pressure and temperature lead me to the conclusion that 

 a difference of 74'26 atmospheres on the manometer 

 represents the variation of pressure corresponding to the 

 condensation of oxygen in the tube immersed in the car- 

 bonic acid. 



** This variation has been exactly observed in the three 

 last experiments which I have made with the assistance 

 of many of my colleagues here at Geneva. 



" The quantity of liquid oxygen which we had in the 

 tube was 45*467 grammes, corresponding to a volume of 

 46-25 cubic centimetres. But it is possible that the 

 highest part of the thin tube had some centimetres in 

 length not occupied by the liquid. This may explain the 

 difference of o"8 gramme found. 



" Moreover, very volatile liquids have such considerable 

 expansions that it is indispensable to have exactly the 

 temperature to which they are subjected, in order to 

 determine their true density. However this may be, 

 there is an absolute verification, within small limits, of 

 error of the theoretical calculation regarding this physical 

 constant." 



In addition to this important result, in another experi- 

 ment, M. Pictet has used polarised light to determine the 

 presence or absence of solid particles of oxygen in the 

 jet. The jet was illuminated by means of the electric 

 light, and observed with two Nicol prisms. A very strong 

 polarisation was observed, indicating the presence of 

 solid particles, which in all probability were really solid 

 particles of oxygen. 



