JvNE 28, 1895.] 



SCIENCE. 



705 



of nitrogen. I will not take up time in go- 

 ing through the experiment, but will merely 

 exhibit a tube already prepared (image on 

 screen). 



One can work more efficiently bj' employ- 

 ing the alternate currents from dj'namo ma- 

 chines whieli are now at our command. In 

 this institution we have the advantage of a 

 public supply : and if I pass alternate cur- 

 rents origiiiating in Deptford through this 

 Ruhmkorft' coil, which acts as what is now 

 called a ' high potential transformer,' and 

 allow sparks from the secondary to pass in 

 an inverted test tube between platinum 

 points, we shall be able to show in a com- 

 paratively short time a pretty rapid absorp- 

 tion of the gases. The electric current is led 

 into the working chamber through bent glass 

 tubes containing mercury, and provided 

 at their inner extremities with platinum 

 points. In this arrangement we avoid the 

 risk, which would otherwise be serious, of 

 a fracture just when we least desired it. I 

 now start the sparks by switching on tlie 

 Ruhmkorfl'to the alternate current supply; 

 and, if you will take note of the level of tlie 

 liquid representing the quantity of mixed 

 gases included, I think j'ou will .see after, per- 

 haps, a quarter of an hour that the liquid 

 has very appreciably risen, owing to the 

 union of the nitrogen and the oxygen gases 

 under the iuHueuce of the electrical dis- 

 charge, and subsequent absorption of the re- 

 sulting compound l)j- the alkaline li(juid 

 ■with which the gas space is enclo.sed. 



By means of this little apparatus, which 

 is very convenient for operations upon a 

 moderate scale, such as for analj'sis of ' nit- 

 rogen ' for the amount of argon that it may 

 contain, we are able to get an absorption 

 of about SO cubic centimetres per hour, or 

 about 4 inches along this test tube, when 

 all is going well. In order, however, to ob- 

 tain the isolation of argon on any consider- 

 able scale by means of the oxygen method, 

 we must employ an apparatus still more en- 



larged. The isolation of argon re([uircs the 

 removal of nitrogen, and, indeed, of very 

 large quantities of nitrogen, for, as it ap- 

 pears, the proportion of argon contained iu 

 atmospheric nitrogen is only about 1 per 

 cent., so that for every litre of argon that 

 you wish to get you must eat up some hun- 

 dred litres of nitrogen. That, however, can 

 be done upon an adequate scale by calling 

 to our aid the powerful electric discharge 

 now obtainable by means of the alternate 

 current supply and high potential trans- 

 formers. 



In what I have done upon this subject I 

 have had the advantage of the advice of Mr. 

 Crookes. who some years ago drew special 

 attention to the electric discharge or flame, 

 and showed that many of its properties de- 

 pended upon the fact that it had the power of 

 causing, upon a considerable scale, a com- 

 bination of the nitrogen and the oxygen of 

 the air in which it was made. 



I had first thought of showing in the lec- 

 ture room the actual apparatus wliich I 

 have employed for the concentration of 

 argon; but the difliculty is that, as the ap- 

 paratus has to be used, the working parts 

 are almost invisible, and I came to the con- 

 clusion that it would reallj' be more instruc- 

 tive as well as more convenient to show the 

 parts isolated, a very little eflort of imagin- 

 ation being then all that is requu-ed iu order 

 to reconstruct in the mind the actual ar- 

 rangements emploj'ed. 



First, as to the electric arc or flame it- 

 self. We have here a transformer made by 

 Pike and Harris. It is not the one that I 

 have used in practice; but it is convenient 

 for certain pur^wses, and it can lie connected 

 by means of a switch with the alterixate 

 currents of 100 volts furni.shed l)y the Sup- 

 ply Company. The platinum terminals 

 that you see here are modelled exactly upon 

 the plan of those which have been employed 

 in practice. I may say a word or two on 

 the question of mounting. The terminals 



