Ken,' Experiments on the fluoric Coinpovrids. 93 



darker and more hea^y than the aslies fiom a tobacco pipe ; 

 that collected from the surface of the sea, when dried, resem- 

 bling a cake of shoe blacking. Several ships in different quar- 

 ters of the Gulpli and River St. Lavvreiice observed the same 

 appearance of darkness, wliich appears to have been pretty ge- 

 neral, although not to the same degree. 



" A frigate coming up, the Captain in his cabin had candles to 

 breakfast at half past eight. No reason can as yet be assigned 

 for this extraordinary phenomenon. It is conjectured by niaiiv to 

 be in cousecpieuce of a volcano ; but the ashes bv no means re- 

 sembled those thrown up by the volcano in St. Vincent. West 

 Indies, some years since ; some of which the writer of tliis has 

 seen. Considerable fogs and hazy weather had prevailed for 

 some time, during which it was supposed the Leopard man of 

 war was wrecked on the Island of Anticosti." 



XVI. ^n yfccounf of some new Experiments on the fluoric 

 Compounds ; with some Observations on of her Objects of che- 

 mical Inquinj. By Sir H. Davy, LL.D. F.R. 'S. V.F. R.I* 



An this paper I shall offer to the Society a continuation of 

 those researches, the details of which have been already ho- 

 noured with a place in their Transiictions ; and I trust, that the 

 experinients and observations which I have to communicate will 

 be found to elucidate some important but obscure parts of che- 

 mical philosophy. 



In the last paper which I had the honour of presenting to 

 this body, I have given an account of a number of experiments 

 made witli a view of decomposing the fluoric acid : the most 

 probable inference, from my results, was, that the pure liquid 

 fluoric acid consists of hydrogen united to a substance which, 

 from its strong powers of combination, has not as yet been pro- 

 cured in a separate form, but which is detached from hydrogen 

 by metals, and which, in union with the basis of the boracie 

 acid and silica, forms the fluo-boric and silicated fluoric gases. 



All the new experiments that I have made on the fluoric 

 compounds tend to confirm this idea ; and the various attempts 

 that I have made, since the last session, to decompose the j)rin- 

 ciple in the fluoric acid separated at the negative surface in \'ol- 

 taic combinations, have been unsuccessful. 



I have found that fluate of lead, the substance formed bv the 

 action of a soluble salt of lead on fluate of potassa or fluate of 

 ammonia, is immediately decomposed, when moist, by ammo- 

 niacal gas, and a white jiowder separates from it, which must 

 contain oxygen, as it gives carbonic acid by being ignited with 

 • 1 roni tlie Philosojjliical Transactions for 181 1, part i. 



charcoal 



