256 



Mr. G. Gore on Hydrofluoric Acid. 



[Jan. 28, 



homologies of the various parts of the ova of mammals and the eggs of 

 birds and lower animals. Chemically the corpus luteum is the homologue 

 of the velk, genetically it is nearly so ; but its use and destiny are totally 

 different. 



Note. — The foregoing researches are technical parts of inquiries carried 

 on by the author at the Pathological Laboratory, St. Thomas's Hospital, 

 for the Medical Department of the Privy Council, in continuation of re- 

 searches already published in the Ninth and Tenth Reports of the Medical 

 Officer of the Privy Council. 



The special thanks of the author are due to Dr. Hooker, Director of the 

 Royal Botanical Gardens, Kew, for the kindness and liberality with which 

 he supplied, through Mr. Smith, the Curator, most of the botanical speci- 

 mens examined in the course of this research. 



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

 November 14, 1868. 

 (Abstract.) 

 A. Anhydrous Hydrofluoric Acid. 



This paper contains a full description of the leading physical and che- 

 mical properties of anhydrous hydrofluoric acid, and also an account of 

 various properties of pure aqueous hydrofluoric acid. The author obtained 

 the anhydrous acid by heating dry double fluoride of hydrogen and potas- 

 sium to redness in a suitable platinum apparatus (shown by a figure ac- 

 companying 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 care- 

 fully verified by various methods of analysis, both of the double fluoride 

 from which it was prepared and of the acid itself ; and particulars are given 

 of all the circumstances necessary to insure reliable and accurate results. 

 Nearly all the operations of preparing, purifying, analyzing, and examining 

 the properties of the acid were conducted in vessels of platinum, with lu- 

 tings 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 requires 

 the most extreme degree of care in its manipulation. It is a perfectly co- 

 lourless and transparent liquid at 60° Fahr., very thin and mobile, extremely 

 volatile, and densely fuming in the air at ordinary temperatures, and ab- 

 sorbs water very greedily from the atmosphere. It was perfectly retained 

 in platinum bottles, the bottle having a flanged mouth with a platinum 

 plate secured with clamp-screws, and a washer of paraffin. 



