NUCLEAR CONDENSATION OF CERTAIN ORGANIC VAPOURS. 
453 
n-Butyric acid was fractionated once, and the portion (nearly the whole of the 
original) boiling between 162 0- 5 and 162° - 6 was used (162°'*4 Richardson). 
Iso-butyric acid was fractionated. Boiling-point 152°*1 to 152 0, 6 (1 53° 
Richardson). 
Iso-valeric was treated with phosphorus pentoxide, and twice distilled. Boiling- 
point 175° to 176° (175°*3 Richardson, 174°'9 Schmidt, 174°*5 Landolt). 
Amyl alcohol: Kahlbaum’s (pyridine free) “ inactive,” 
(CH 3 ) 2 CH-CH 2 -CH 2 -OH, 
was fractionated. Boiling-point 130 o, G to 131° (131 0, 4 Thorpe, 132° Young and 
Fortey, 130 o, 3 Schmidt). Some optically active alcohol was present in the final 
fraction which gave [a] D = — 0 o- 5 ; for active amyl alcohol [a] D = +5 0- 2. 
Least Expansion for Condensation in Air of an Organic Vapour exposed to 
Rontgen Rays. 
The test-tube expansion chamber of glass and mercury, already described (see fig. 2), 
was used to find the least expansion to produce condensation in a mixture of air and 
an organic vapour when exposed to Rontgen rays. The air in the carefully cleaned 
apparatus was dried by placing an open tube containing phosphorus pentoxide 
inside B (fig. 1). In removing this tube less than 1 mgrm. of water as vapour gained 
admission to the apparatus. The organic liquid was then admitted by means of the 
stop-cock funnel (fig. 2) to above the mercury. 
The dust present in the apparatus settled out on standing the vessel (say) overnight. 
It was more quickly removed by small expansions. It is worthy of remark that some 
vapours could be freed from dust by the latter method distinctly more quickly than 
others. Thus four or five expansions freed air and ethyl propionate from dust, while 
air and water vapour have always taken more expansions than that. 
Since the writer has found, certainly in the case of some vapours, that the least 
expansion for condensation depends slightly on the intensity of the Rontgen rays, it 
is necessary to roughly specify the intensity of the rays used in the experiments to be 
described. A large bulb with a heavy water-cooled anti-cathode driven by a Marconi 
induction-coil was used as the source of the Rontgen rays. The alternative spark gap 
was from 5 to 10 cms. The anti-cathode was 46 cms. from the expansion chamber. 
The rays had to penetrate the wall—about 0’08 cm. thick—of the glass test-tube 
expansion chamber. 
With some vapours the drops obtained were very minute, so were not readily seen, 
and did not settle out quickly. With such a vapour it was necessary, after an 
expansion giving a number of drops, to either wait some time for them to settle out, 
