19 



B. APPARATUS DESIGNED FOR SPECIAL INVESTIGATIONS. 



97. Apparatus for preparing small quantities of liquid 

 carbon dioxide, or liquid hydrochloric acid gas, and 

 examining its action upon various substances. 



1876. Lent by George Gore, F.R.S. 



(Philosophical Transactions of the Royal Society, 1861, and 

 Proceedings of the Royal Society, Ma}' 1865.) 



98. Vessels and Articles of baked and fused fluoride, 

 cryolite, fluor-spar, native graphite,, gas carbon, and 

 wood charcoal, for researches on Fluorides. 



1876. Lent by George Gore, F.B.8. 



99. Portable differential barometers (2) used by Prof. 

 Mendeleef in his investigations on the tension of gases. 

 See Transactions of the Imperial Russian Technical 

 Society, 1875. 



1876. Lent by Prof. Mendeleef, St. Petersburg 



100. Pasteur's bottle with funnel-shaped stopper. 

 Price Is. 



1886. Exhibited by Townson fy Mercer. 



101. Pasteur's tubes (2). Price Is. each. 



1886. Exhibited by Townson fy Mercer. 



102. Pasteur's flasks (3) ; one of 125 c.c.'s capacity, 

 and two others of 36 ozs. capacity. 



The latter form of flask was used by Pasteur in his 

 researches upon grape fermentation. Prices Sd. and 3s. 

 1886. Exhibited by Townson Sf Mercer. 



103. Iridio-platinum apparatus to illustrate the mode 

 of preparing anhydrous hydrofluoric acid and the electro- 

 lytic method of obtaining fluorine. 



E. 17. 1888. Made by Johnson, Matthey $ Co. 



The apparatus consists of a platinum U-tube, with fluor-spar 

 stoppers and platinum delivery tubes, the positive electrode 

 consisting of an alloy of platinum with 10 per cent, of indium. 

 Potassium hydrogen fluoride prepared by Fremy's method dried 

 at 100 and then over sulphuric acid and potash in a vacuum 

 is used ; this salt is much less deliquescent than the normal 

 fluoride. The dried salt is heated in the platinum retort and the 



