170 Friedel 4nd Crafts on the Ethers of Silicic Acid. 
The normal ether began to boil at 55° and the thermometer rose 
rapidly to 72°-73° and remained neawly stationary at this tem- 
perature (in another experiment at 74°-75°) during the distilla- 
tion. When the distillation was interrupted and recommenced, 
ebullition commenced always at a much lower point than 79°. 
According to this, the diminution of pressure to 8-5 mm. lowers 
distilled at 233°-8°, in the air distilled at 226°-230° under a pres- 
sure of 3-5 mm. + For this Jatter product, the limits of tempera- 
ture within which the thermometer varies during a distillation 
in vacuo, are much less than for normal ether. 
The ebullition is much more regular under a somewhat greater 
pressure, and for this reason and also because we hoped that the 
change of pressure might facilitate the separation of the pro- 
ducts, as Roscoe has observed in the case of hydrates of acids, 
we made another series of distillations under a pressure of 60 
millimeters of mercury. 
These distillations were made with an apparatus which per- 
mitted us to operate almost as rapidly as when distilling in the 
air, and it only requires a small hand pump, when no better 1s 
to be procured. 
The opening B has an india-rubber tube through which 18 
passed the glass tube leading from the flask containing the sub- 
stance. At C a thermometer is introduced in the same way: 
The lower end, A, of the receiver has a tube, which is closed 
during the distillation, and is opened to draw off the product 
when required. It is not necessary to surround the receive! 
