16 THE VOYAGE OF H.M.S. CHALLENGER. 



The woodcut shows well how apparatus of the kind can be fixed and used on board 

 ship. The aspirator and the condenser were kept steady by blocks bearing against the 

 table battens. It shows also a convenient way of keeping bent tubes and other light 

 articles, which are held up by a piece of india-rubber tube, slit lengthwise, and attached 

 to the beam by a tack. An india-rubber clamp is thus formed sufficiently strong to 

 retain any small article of suitable shape. Long tubes may be supported by more than 

 one clamp. 



For a particular description of the method of determining the carbonic acid by this 

 apparatus, the reader is referred to the special memoir on the subject. 1 In this place it 

 will be sufficient if the nature of the method is briefly indicated. The sample of sea 

 water freshly drawn was brought into the flask a, and mixed with a saturated solution 

 of chloride of barium in sufficient quantity to precipitate the sulphates. Heat was then 

 applied, and the contents of the flask distilled off to very near dryness in a current of air 

 freed from carbonic acid. The carbonic acid liberated from the water was retained by 

 the baryta- water in the . receiver c, and U-tubes d, d. Its amount was determined by 

 measuring the baryta remaining in solution. 



An ingenious modification of Bunsen's apparatus, by Jacobseu, was used for boiling the 

 atmospheric gases out of the water (see fig. 8). It consists of three principal parts — the 

 flask, the bulbed tube, and the receiver for the gases. The flask is spherical, with a strong 

 welted lip, and holds about 900 c.c. The peculiarity of the apparatus consists in the form 

 of the bulbed tube, and in its connection with the flask. The bulb a, in which the water 

 is boiled to expel the air from the apparatus, is of the pear shape represented in the figure, 

 in order to have the exit tube as nearly as possible at its highest point, so as to prevent 

 the accumulation of any air in its upper part. Its capacity is about 60 c.c. The lower 

 end of the tube is closed, but about half an inch from the end it has a very small hole c 

 in the side. The perforated india-rubber cork d fits the neck of the flask accurately, and 

 through the perforation the tube passes air-tight and with some friction. The receiver b holds 

 from 50 to 60 c.c, and has the entry and exit tubes contracted as shown in the figure. It is 

 joined to the bulbed tube by an air-tight india-rubber connection, and carries at its exit 

 another piece of tubing, for a purpose to be mentioned presently. The upper part of the 

 apparatus is supported by the clamp m, and by the bent rod f, which is clamped firmly 

 on the lower part of the bulbed tube. The flask is supported in the water-bath g 

 by the clamp h attached to the retort-stand k, which in its turn is lashed to the blowpipe 

 table. 



When the apparatus is to be used, a sufficient quantity of boiled distilled water is 

 introduced into the bulb, and the cork d pushed over the opening c. The sea water to be 

 examined is run directly into the flask from the deep-sea water bottle, through a tube with 

 a narrow opening reaching to the bottom of the flask, the tube being gradually withdrawn 



1 Dittmar, Phys. Chem. Chall. Exp., part. i. p. 103, 1884 ; see also Joum. Cliem. Soc, p. 464, 1878. 



