AND RATIO OF THEIR ATOMIC WEIGHTS. 83 



used. After the measurement had been made, tliey were to meet in a vacuous ap- 

 paratus at two platinum jets and be mostly combined. The I'osidne, when the 

 pressure was too small I'oi' eon)bustion to continue, was to be transferred by a self- 

 acting leakage-proof Toepler air [lump to a eudiometer, where eight hundred cubic 

 centimetres of electrolytic gas have 1)een safely ex[)loded. After all but ten cubic 

 centimetres had been exploded in this way, the residue was to ])e transferred from 

 this eudiometer to a common Bunseu eudiometer, and analyzeth The apparatus is 

 set up, ready for use, and it has beeu used, though no experiment has been fin- 

 ished, and thei'e is no difHculty in its use, and since so much is self-acting it is not 

 very laborious. But, as I have not had time uninterrupted enough, nor nerves 

 steady enough, to finish, without assistance as I am, even a single experiment, the 

 apparatus had to be broken up, unused, for lack of room. 



The apparatus which is nearly ready is designed to measure in tlie same ves- 

 sel three nearly equal volumes of hydrogen and oxygen, each of about 2.6 litres, 

 and to combine them by combustion from platinum jets in a space containing a part 

 of the measured volume, and afterwards to transfer the remainder to a eudi- 

 ometer for analysis. It is completed, except building a pier and })utting together 

 the apparatus ; wdiether it will be used is doubtful. 



The third method, which, Avith the apparatus already set up for other pur- 

 poses, was easiest to cari'y out, has been successfully employed in a series of ten 

 determinations. Unfortunately, it is that one of the three whicii, on account of 

 the uncertainty in some of the constants needed in the reduction of ol)servations, is 

 the least helpful. The ex[)eriments l)y this method will now be described. 



2. METHOD EMPLOYED. 



It will be recalled that Leduc made two experiments, in w hich he decom[)Osed 

 an alkaline hydroxide by electrolysis, and measured the density of the mixed gases. 

 From this could be computed the ratio of the volumes of the components. 

 No determination seems to have been made whether the electrolytic mixture would 

 recombine without residue ; which very much needs proof in any experiment chinn- 

 ing precision. If the numbers given in Comptes Eendus, August, 1892, page 31 o, 

 are correctly printed, the reduction fails to take into account the physical conditions 

 involved. 



Having the apparatus with which the fifth series of determinations of the 

 density of hydrogen was made, I resolved to make a determination by means of 

 the |)rocess used by Leduc, but with material modifications. One consisted in 

 avoiding the contamination of the gas with mercurial vapor, by weighing, not a 



