Alternating Current in a Chemical Laboratory. 117 
Notice whether there is a perceptible odor at upper end of 
small glass tube and whether anything collects on the glass of 
either tube. All volatile substances that condense at ordinary 
temperatures and all perceptible odors will be noticed in a few 
seconds. The operator can soon determine whether the analysis 
should be continued with the high heating arc or the milder 
heat of an ordinary blow pipe. 
The range of blow pipe work is thus increased to a consider¬ 
able extent. 
Some experiments on the synthesis of the hydrocarbons from 
their elements have been tried. 
Acetylene is easily prepared by passing hydrogen through or 
along side of the arc contained in the following apparatus. 
Fit a gas tight cork into each end of a straight lamp chimney. 
Pass brass tubes 1 cm. diameter and 15 cm. long through each 
cork. 
Into one end of each brass tube put a tube of carbon 3 cm. 
long. These tubes are made by boring out the core of a cored 
carbon with a steel wire. 
This operation is slow, but after a tube is prepared it will 
last through many experiments. 
The joints of the carbon and brass tubes should fit tightly and 
be sealed with a mixture of charcoal and sugar syrup dried and 
charred or of graphite and water. 
Fit the corks and brass tubes so the ends of the carbon tubes 
are nearly together, test the apparatus for gas leakage turn on 
current and again test after the heat has reached a maximium. 
If air tight, pass a stream of hydrogen through the brass and 
carbon tubes. After the oxygen in the apparatus has been con¬ 
sumed it may be necessary to increase the current as hydrogen 
seems to extinguish the arc. The author hopes to find the 
cause of this soon as several facts suggest an explanation. 
Acetylene passes over mixed with hydrogen and small quant¬ 
ities of an oil resembling benzene. 
The latter is generally present in very small quantities and 
as it is known that acetylene passes into benzene at the high 
temperatures it is not surprising that it is found here. 
The yield of acetylene seems to be about the same as by the 
