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Mr. W. N. Hartley. [May 9, 



VI. " On Films produced by Vaporised Metals and their 

 Applications to Chemical Analysis. — Preliminary Notice."' 

 By W. N. Hartley, F.R.S., Royal College of Science, 

 Dublin. Received April 22, 1889. 



Having recently communicated to the Royal Dublin Society 

 (March 20fch) a paper entitled " On the Constitution of the Electric 

 Spark," I have described a means of obtaining deposits of metals and 

 of metallic oxides, which serves as a very delicate test for some of the 

 metals. It has been considered desirable to devote much further 

 study to the subject, and a method of working has been devised which, 

 so far as it has been applied, appears to be especially useful in the 

 examination of certain metallurgical products, as for instance in the 

 detection and even estimation of the precious metals in copper, lead, 

 and tin, and of certain impurities in copper. The method may be stated 

 to be carried out in the following manner : — 'Electrodes of the metals 

 to be tested are put into communication with the wires of an induction 

 coil used for the production of condensed sparks, such as serve for 

 the photographing of the ultra-violet spectra. When a plate of mica 

 through which a series of pin-holes has been pricked is placed in the 

 path of the spark and the current is passed for a period varying from 

 5 to 10, 15, 20, 30, and 60 seconds, a series of deposits of different 

 degrees of tenuity are obtained, which are metallic with the noble 

 metals, such as silver, gold, palladium, iridium, and platinum, and are 

 oxides with such metals as are oxidisable, for instance magnesium, 

 zinc, cadmium, lead, tin, copper, iron, nickel and cobalt, aluminium, 

 indium, thallium, arsenic, antimony, and bismuth. 



Gold gives films of extreme tenuity and beautiful in richness of 

 colour, partly deep red or rose-tinted, but chiefly of a magnificent 

 blue, with a shade of green in the thinnest part of the deposit. 



Silver gives yellow films, while palladium, iridium, and platinum 

 give different shades of brown. The films are different as to the 

 area which they cover, the difference being due to the volatility and 

 the colouring power of the metals. Gold is by far the most remark- 

 able in this respect. The colours of the oxides, such as various shades 

 of brown with, iron, cobalt, nickel, thallium, cadmium, bismuth, and 

 yellow with zinc and lead, serve as tests by which they can be recog- 

 nised. The volatility of the oxides is also a distinctive feature ; arsenic 

 forms a remarkable series of rings round the pin-hole, and other 

 metals, antimony standing next, are thus distinguishable. 



It is stated in the paper already quoted that beside the metallic 

 deposit which silver gives, there is a yellow colour and a tinge of rose 

 colour and violet. The silver employed was originally prepared by 



