422 ME, T. GEAHAM ON THE ABSORPTION AND 



cylindiical furnace. The porcelain tube was fitted at both ends with perforated corks, 

 well cemented with fused gutta percha, and provided each with a small quill tube. Such 

 may be described as the distillatory apparatus employed. It was connected at the end 

 N with the Sprengel pump A B, to be used as an exhauster and transferrer of gas, by 

 means of good caoutchouc adapters (not vulcanized), and at the other end, M, wiih the 

 apparatus for supplying dry hydrogen, atmospheric air, or any other gas. By a screw 

 clamp upon the adapter at M, the tube could be closed, and the gas-producing apparatus 

 then detached, leaving the porcelain tube shut at one end. A tube of the hard glass 

 used in combustion analysis, may be substituted for the porcelain tube in many such 

 experiments. A less degree of heat suffices than was at first supposed. 



The porcelain tube is exhausted by continuing the action of the Sprengel for ten or 

 fifteen minutes, till small bubbles of gas cease to be delivered by the tube A B in the 

 mercurial trough below. The sufficiency of the joints is thus first ascertained. Heat 

 being then applied to the porcelain tube, its impermeability at a red heat will also be 

 tested. 



The platinum, when introduced, was confined to about two-thirds of the central por- 

 tion of the porcelain tube, which could be conveniently heated. The apparatus obvi- 

 ously aff"ords the means both of heating the platinum in a vacuum and also in an 

 atmosphere of hydrogen or any other gas admitted into the interior of the porcelain 

 tube at M. 



Fused platinum. — Articles of manufactured platinum appear now to be prepared 

 exclusively from the fused metal. 



1. A quantity of clean platinum wire from fused metal, measuring 0'695 metre in 

 length, 4'1 millims. in diameter and 201 grms. in weight, was bent and introduced into 

 the porcelain tube, which was then exhausted. The platinum was first heated alone for 

 an hour to drive off any natural gaseous product, and then dry hydrogen gas was 

 admitted to the porcelain tube, the gas being evolved from pure sulphuric acid and 

 pure zinc. The hydrogen was conveyed in excess into the porcelain tube, at a cherry- 

 red heat, and the temperature was then allowed to fall in a gradual manner — a pro- 

 cedure which was found to promote the absorption of the gas. The platinum was thus 

 retained for about twenty minutes in an atmosphere of hydrogen, at a temperature 

 partly above and partly below dull redness, terminating with the lower temperature. 

 After the fire was withdrawn and the tube allowed to cool, air or nitrogen was driven 

 through it, and all free hydrogen thus expelled from the apparatus. 



The closed tube was now exhausted in the cold, but no hydrogen came off. The 

 platinum being still retained in a good vacuum, heat was again very gradually applied, 

 and the action of the Sprengel pump maintained. Simultaneously with the first 

 appearance of visible ignition, gas began to be evolved. In one hour, the porcelain tube 

 being heated to redness, 2*12 cub. centims. of gas were collected, of which about one- 

 third was collected in the first ten minutes. It was found, by explosion with oxygen, 

 to consist of — 



