﻿470 



Royal Society : — 



Liquid. 



Specific 

 resistance. 



Water 1- 



Glycerine 3-84 



Acetic acid (glacial) 8 - 38 



Acetone 8*51 



Oxalate of ethyl 8-85 



Sperm-oil 8*85 



Alcohol 908 



Acetate of ethyl 9-08 



Nitrobenzol 9*86 



Oxalate of amyl 1O06 



Butylic alcohol 10*00 



Liquid. S P e f cific 



u resistance. 



Acetate of amyl 10-00 



Amylamin 10-14 



Amylic alcohol 10-23 



Oil of turpentine 11-75 



Nitrate of butyl 11-87 



Chloroform 12*10 



Bichloride of carbon 12*92 



Mercury amyl 12-92 



Bromide of ethylen 13*16 



Iodide of amyl 1327 



Iodide of ethyl (?) 



The more salient points of these results are pointed out, such as 

 the preeminently small resistance of water and of bodies containing 

 a large proportion of the elements of water (potential water), the 

 possible connexion of this fact with the results of Magnus concern- 

 ing the conductivity of hydrogen, the increased resistance accompa- 

 nying increased molecular complexity in the case of isotypic liquids 

 as exemplified by the alcohols and their derivatives, the great re- 

 sistance shown by the liquids containing halogens. The results ob- 

 tained by Tyndall in regard to relative diathermancy are shown to 

 be in accord with the author's results concerning resistance. A 

 highly diathermanous liquid invariably offers great resistance to 

 conducted heat. The relation between electrical and thermal resist- 

 ance in the case of liquids is also briefly discussed. 



Jan. 28. — Lieut. -General Sabine, President, in the Chair. 



The following communication was read: — 



" On Hydrofluoric Acid." By G. Gore, F.R.S. 



A. Anhydrous Hydrofluoric Acid. 



This paper contains a full description of the leading physical and 

 chemical properties of anhydrous hydrofluoric acid, and also an ac- 

 count of various properties of pure aqueous hydrofluoric acid. The 

 author obtained the anhydrous acid by heating dry double fluoride of 

 hydrogen and potassium to redness in a suitable platinum apparatus 

 (shown by a figure accompanying the paper), and states the conditions 

 under which it may be obtained in a state of purity. 



The composition and purity of the anhydrous acid are shown and 

 carefully verified by various methods of analysis, both of the double 

 fluoride from which it was prepared and of the acid itself ; and par- 

 ticulars are given of all the circumstances necessary to insure reliable 

 and accurate results. Nearly all the operations of preparing, puri- 

 fying, analyzing, and examining the properties of the acid were con- 

 ducted in vessels of platinum, with lutings of paraffin, sulphur, and 

 lampblack ; articles of transparent and colourless fluor-spar were also 

 employed in certain cases. Nearly all the manipulations with the 

 acid were effected while the vessels containing it were immersed in a 

 strong freezing-mixture of ice and crystallized chloride of calcium. 



The pure anhydrous acid is a highly dangerous substance, and 



