102 Gooch and Phelps—Precipitation and 
_ per to a small bulb. The absorbtion cylinder consists of a 
wide glass tube, (C) fitted at either end with a rubber stopper. 
The stopper at the lower end of the cylinder, placed vertically, 
carries a short tube, about 1°5™ in diameter, to which is 
secured a smaller rubber balloon. The cylinder and balloon 
together hold about 100 cm*. The upper stopper is perforated 
with two holes, through one of which passes the tube-of a 
glass stop-cock, while through the other hole passes a long 
tube reaching to the interior of the balloon and provided with 
a valve (V)—preferably a modified Bunsen valve, of the pat- 
tern recently devised by Kreider and described on p. 132 of 
this number. 
In using this apparatus a saturated solution of barium 
hydroxide (which is made hot, filtered into a siphon-bottle, . 
and preserved from atmospheric action by a floating layer of 
kerosene) is introduced by pressure upon the air in the siphon- 
bottle or by suction applied to the stop-cock of the cylinder. 
Such a solution contains about five per cent. of its weight of 
the hydroxide, and we find it best to use in every case an 
amount at least a fourth in excess of the quantity theoretically 
required to absorb the carbon dioxide, and to fill the cylinder 
and balloon nearly full of liquid. The carbonate is weighed, 
introduced into the flask, and washed down with fifteen or 
twenty cubic centimeters of boiled water, which is protected 
in the wash-bottle from carbon dioxide in the breath by a bal- 
loon attached to the inlet tube. A smali tube holding enough 
hydrochloric acid to effect the decomposition of the carbonate 
to be analyzed, is placed in upright position in the evolution 
flask. The stopper is inserted in the flask and connections are 
made as shown in the figure, the little tube containing the acid 
is overturned by inclining the flask, the acid mixes with the 
water and effervescence begins. Heat is applied and the liquid 
in the flask is boiled until that in the cylinder is heated by the 
steam nearly to the boiling point, in order that the precipitated 
barium carbonate may become as granular as possible. The 
carbon dioxide evolved and the air in the flask are transferred 
in the process to the absorbtion cylinder, the valve serving to 
prevent the back-flow of the liquid while the balloon expands 
to give room to the air and condensed steam. When the boil- 
ing is done the flask and tube are disconnected at the rubber 
joint, the cylinder is shaken to insure the absorbtion of the 
carbon dioxide, and the liquid carrying the greater part of the 
precipitate is transferred through the stop-cock to a filter care- 
fully fitted to its funnel, moistened with water and containing 
about 5 em® of xylene, (which we found to be preferable to 
benzene, kerosene, or amyl alcohol, the function of which is 
to rise to the surface when the aqueous solution is added so as 
