34 PRESIDENT’S ADDRESS. 
which at ordinary temperature it acts with explosive 
violence. Cooled wood placed in it is untouched, but if a 
drop of the liquid fall on to the floor it bursts into flame. 
Tron, silicon, boron, sulphur, and phosphorus, and other 
substances placed in liquid fluorine, after previous cooling 
in liquid oxygen, do not burst into flame as they do in the 
gaseous fluorine, but solid benzene and turpentine are 
decomposed with incandescence and explosive violence. 
The boiling-point of liquid fluorine is —187°; its density 
is 1:14; it is soluble in all proportions in liquid air and 
liquid oxygen. It does not solidify at —210°, and has 
not yet been solidified. It has no absorption spectrum, 
and is not magnetic. At —190° it has no action on dry 
oxygen, water, or mercury, but reacts with incandescence 
on hydrogen. 
By passing fluorme through liquid oxygen an explosive 
powder is produced; a hydrate of fluorine seems to be 
produced from the minute crystals of ice present in the 
liquid oxygen. 
There are many other interesting points about fluorine 
still to be worked out. 
At the Chemical Society, on November 4, Professor 
Dewar, after the paper upon liquid fluorine, gave another 
paper upon the liquefaction of air and the detection of 
impurities init; even after careful filtration liquid air yields 
a deposit of solid carbon dioxide, and some organic matter ; 
liquid air is always turbid unless perfectly pure. 
He liquefied 80 litres of gas from a spring at Bath; the 
liquid was turbid, and a yellowish brown carbonaceous 
petroleum-like body was obtained from it; no trace of 
oxygen was found in the gas, but argon was present. 
Helium was found to be present in the original gas in the 
proportion of 1 in 1,000, and was left as a non-liquefiable 
residue. 
