490 Mr. J. Y. Buchanan on the Absorption of 



through a hole in the sash. The flask containing the sea-water is sup- 

 ported on a ring, by a clasp holding its neck. Both of these, along with 

 the spirit-lamp underneath the flask, are attached in the usual way to an 

 iron rod, which is attached to the projecting side of the ship by an eye- 

 bolt, in which it has a play of rather more than an inch in the direction 

 of its length. The lower end of the rod sits securely in a hole, let into 

 the top of the working-table. When the apparatus is dismounted the rod 

 is pushed up, till its lower end has freed itself from the hole and laid 

 flat along the roof, being supported at one end by an eye-bolt, at the 

 other by a hook. The aspirator and the condenser are retained in their 

 places by wooden blocks, which fit in between them and the ship's side or 

 the battens on the bench. 



The water in which the carbonic acid is to be determined is introduced 

 into the flask by means of a tube reaching to the bottom. When the 

 carbonic acid is to be determined in a specimen of water, the apparatus is 

 first put together and a current of air, free from carbonic acid, drawn 

 through, care having been taken to see that it is thoroughly dry in all its 

 parts. The corks in the receiver and V-tubes are then eased, and 

 from 15 c. c. to 20 c. c. baryta-water, usually of about ^ normal 

 strength, run into them. The water to be examined is introduced into 

 the flask through a tube reaching to the bottom ; 10 c. c. of a nearly 

 saturated solution of chloride of barium are then added, the apparatus 

 closed and heat applied. When the liquid begins to boil, care must be 

 taken to lower the flame to avoid frothing over. A gentle current of 

 air is now conducted through the boiling liquid, and the receiver con- 

 stantly agitated. After half an hour's boiling, about 100 c. c. water 

 have distilled over, and at the same time all the carbonic acid. That 

 the latter is the case, I ascertained by changing the baryta-water at this 

 point, and continuing the distillation, when no turbidity was produced. 

 That, at any rate, no appreciable amount of carbonic acid passes after 

 even the first 50 c. c. water have been distilled over, may be very easily 

 seen by the liquid in the receiver passing from a turbid, somewhat 

 frothy solution, to a clear one, in which a well-defined precipitate is sus- 

 pended, and whose amount does not visibly alter as the distillation 

 proceeds. Although such is the case, I have usually, as it costs but 

 little more time and trouble, carried on the distillation until seven 

 eighths have passed, and indeed, in many cases, until crystallization has 

 commenced. When proper attention is paid to the agitation of the 

 receiver during the first part of the distillation, the amount of carbonic 

 acid reaching the first V-tube is quite insignificant, and the baryta- 

 water in the second remains perfectly clear. When this operation is 

 finished, the contents of the V-tubes are washed into the receiver with 

 boiled water, and the remaining alkalinity determined with hydrochloric 

 acid of known and convenient strength. The point of neutralization is 

 indicated by rosolic acid. 



