16 
responsible for the phenomena observed. It has been observed by 
these and other investigators that when a jet of steam emerges from a 
small orifice into dust-free air. there is very little if any condensation 
to be observed within half an inch or so of the orifice. On the other 
hand, if an electrode from which electricity is escaping be placed near 
the origin of the jet, dense condensation occurs right up to the orifice, 
and the jet itself appears colored, the color being due to the scattering 
of light by a great number of very small particles of water, the diame- 
ter of which is very small compared with the wave length of light. 
According to J. J. Thomson ( 422 ), the electricity which escapes into 
the gas is carried by the charged atoms of the gas, and since in the 
region immediately around these atoms there will be a very intense 
electric field there will be a tendency for the steam to deposit in these 
regions. Thus around these charged atoms there will be very small 
drops of water, which will scatter the blue light more than the red, so 
that the jet when seen by transmitted light will appear reddish. 
Von Helmholtz and Richarz ( 208 ) found further that condensation 
in the steam jet is also brought about by chemical action going on 
in its neighborhood. The reactions investigated were of the most 
varied character, involving such processes as the combination of nitric 
oxide and oxygen, ammonia, and hydrochloric acid, the oxidation of 
phosphorus, sulphur, and other readily combustible substances. All 
of these were found not only to effect the condensation of live 
steam, but also to cause the condensation of other vapors, such as 
those of alcohol and acetic acid. As a matter of fact so univer- 
sal is this influence that Von Helmholtz and Richarz proposed to 
employ the steam jet as a means of detecting ionic dissociation in 
gases. Thus Von Helmholtz ( 207 ) found that condensation is effected 
in the steam jet by various glowing metals, such as platinum foil 
which had been heated to redness and which had not been artificially 
electrified. Similarly other metals such as silver, iron, copper, etc., 
after heating in the flame, color the steam jet for a long time. This 
is also shown in a high degree by all glowing organic bodies, such as 
wood, paper, tobacco, and especially by glowing sulphur. It was also 
proved that the production of smoke has nothing to do with the phe- 
nomenon observed. Tobacco smoke, especially, was observed to be 
without influence. Von Helmholtz and Richarz ( 208 ) found that con- 
densation in the steam j et could be brought about by a piece of glow- 
ing phosphorus at a distance of several decimeters away, and that at 
this distance it acted remarkably powerfully, but less actively, on the 
vapors of alcohol, anilin, formic, and acetic acids. They also proved 
that the thick white clouds which are produced when moist phosphorus 
is exposed to the air or oxygen do not exhibit this phenomenon when 
the glowing phosphorus is quenched. So, also, the oxidation products 
of phosphorus already prepared had no influence on the condensation. . 
