46 ALCOHOL, SPIRIT OF WOOD, AND ETHERS. 
alcohol ; finally the residue of the distillation always contains 
a resinous matter or carbon, and the chlorides are reduced to 
proto-chlorides. 
The fluoride of boron changes spirit of wood into common 
methylic ether, difficult to condense. This ether is never dis- 
engaged in an isolated state, but always combined with fluoride 
of boron, from which it separates on contact with water. 
The fluoride of silicon does not yield ether with spirit of 
wood any more than with alcohol. 
4. The fourth part of my essay has relation to the action of 
anhydrous sulphuric acid upon absolute alcohol. I have proven 
that, contrary to the received opinion, dry sulphuric acid can- 
not transform absolute alcohol into ether, and I have ascer- 
tained the condition under which this change takes place. 
I have ascertained that a mixture of 2 atoms of anhydrous 
sulphuric acid and 1 atom of absolute alcohol never yields 
ether, but, that on using a mixture composed of 1 atom of 
each, etherification takes place at ordinary temperatures, that 
is to say at 140° to 160°. When a much larger proportion of 
alcohol is used, the excess distils over before etherification ; 
but when the quantity of acid is slightly increased a much 
greater quantity of ether is obtained. The proportions which 
have given the most ether are, 4 atoms acid to 3 absolute alco- 
hol. 
Etherification takes place but incompletely with anhydrous 
phosphoric acid, and only when the alcohol is in excess. 
Anhydrous spirit of wood yields with anhydrous sulphuric 
acid, methylic ether, when the spirit of wood is in excess. 
The most simple manner of accounting for etherification, 
both in relation to the chlorides and to the anhydrous acids, con- 
sists in assimilating the decomposition of the neuter or even 
basic alcohol compounds, to the decomposition of many of the 
salts of ammonia, which, from being neutral, pass by the ac- 
tion of heat to acid salts, on losing ammonia ; with this dif- 
ference, however, that when the alcohol is displaced at the 
temperature of 140 or 150, it is changed into ether and wa- 
ter. The water is partly retained by the acids, and may even 
