-4 HYDROGRAPHY. 



When the lamp has been lighted 20—25 minutes, it is put out H 6 is opened. The mercury 

 rises in A driving the water before it, and this again the boiled-out gases. The mercury-receiver is 

 now raised to such a height that the air gets under a higher pressure than that of the atmosphere. 

 H is opened with communication between C and B t . The air that has been boiled out is driven 

 further on through AT into 2?,, sea-water is allowed to follow and fill the tube K down to the zero- 

 point for the divisions on B t . H is closed. The mercury-receiver is sunk till the surface of the 

 mercury is on a level with the bottom af A. H 6 is closed, and the mercury-receiver is put into 

 its place. 



Some sulphuric acid is poured into T z , and part of it is admitted into the boiling-flask by 

 opening the threeway cock H in a suitable manner. The lamp is lighted. A new boiling-out begins, 

 and as long as it is taking place, water is allowed to run into the cooling-water receiver now and 

 then to keep the pressure and the temperature low in the boiling-flask. 



At the same time, the gases transferred to B x are measured. L^ is sunk, so that the gases 

 in the burette are subject to the pressure of the atmosphere. The volume of the gases contained in 

 the burette B, are read together with the temperature of the water-bath and the height of barometer. 

 Z,, is hung up its place, L 2 is sunk, and H x is opened. The air will now through K^ flow into B 2 , 

 followed by water from B t . This water may, after its being used for a while, contain salt water and 

 sulphuric acid, which, however, will not have any injurious effect during the analysis. The air 

 bubbles up through the water in B 2 to the zero -point for the divisions. H t is closed. Potash is 

 poured into T 2 . 7/ 4 is opened. Potash flows into B 2 and absorbs the carbonic acid. 



The boiling-out with sulphuric acid will likewise last 20 — 25 minutes, on which the lamp is 

 put out again. The gases that have been boiled out are driven into B l and measured there, and 

 farther on to B 2 , where the carbonic acid is absorbed. It will be seen then, that nearly all the 

 oxygen and the nitrogen has been expelled at the first boiling, so that the oxidation of the mercury 

 during the boiling with sulphuric acid may be left out of consideration entirely {Otto Pettersson och 

 Gustaf Ekman: «Grunddragen af Skageracks och Kattegats Hydrografi» pag. 17, Anm. 3). Direct trials 

 with repeated boiling without sulphuric acid led to the same result. 



A third and fourth boiling-out was effected to have all the carbonic acid expelled from the 

 sea-water, and the last time, the remaining quantity of this acid was as a rule so small that it could 

 hardly be measured. 



The gases remaining after the absorption of the carbonic acid are now collected in B 2 , where 

 their volume is measured. The temperature of the water-bath is read. By the sinking of Z 3 and the 

 opening of 7/ 2 , the gases get into B s . H 2 is closed. Pyrogallic acid and a solution of potassium hy- 

 drate is prepared in 7" 3 , which is effected by the introduction of pyrogallic acid into the funnel by means 

 of a tea-spoon and pouring potash over it. When H % is opened, the pyrogallic acid & solution of 

 hydrate is running into the burette B i and absorbs the oxygen. For the sake of the reading, rincing 

 with a little clean water is advisable. The gas remaining in Z? 3 after the absorption of the oxygen, 

 is regarded as nitrogen. Its volume and temperature is determined. The height of barometer is con- 

 sidered as constant during the whole of the analysis. 



Every time that gas is led from one of the burettes to another, it is accompanied by a little 



