468 T. M. Chatard — The determination of Water and 



Art. XLVII. — The Determination of Water and Carbonic 

 Acid in Natiiral and Artificial Salts; by Thomas M. 

 Chatard. 



The following method and apparatus having been used for 

 the analysis of a large number of natural and artificial alkaline 

 carbonates, have been found to give results which are satisfac- 

 tory not only as to accuracy but also as to ease and rapidity. 



A is a combustion tube drawn out and bent at a right angle, 

 B is a platinum boat which contains the salt to be examined 

 and rests upon the thin sheet of asbestos paper C used to pre- 

 ^^^^ ^ ^^ ^ vent adhesion between the 

 . S^^SS^h^" 1 ^^^ platinum and the glass when 

 heated. D is a roll of asbes- 

 tos paper wrapped with thin 

 platinum wire, which fits 

 loosely in the tube and pre- 

 vents back-currents of air during the heating. The bent end of 

 the combustion tube enters one limb of the U-tube E which is 

 my own form and differs, as shown by the drawing, from those 

 at present on the market, by having an especially large bulb at 

 the bottom. The two limbs of the tube are filled with glass 

 beads wet with strong sulphuric acid. Sufficient acid should 

 be put in to fill the narrow tubes up to the bends, compelling 

 the air-current to bubble through. 



In using the apparatus the combustion tube is thoroughly 

 heated and then allowed to cool, a current of perfectly dried 

 air being continually passed through it and the part of the tube 

 where the boat is to be placed being protected by a semi-cylin- 

 drical trough of sheet iron lined with asbestos paper. The U- 

 tube, having been weighed, is now attached to the combustion 

 tube as shown and the air current is regulated. The platinum 

 boat, previously heated and then cooled in a desiccator, is 

 weighed and about one gram of the salt put into it and 

 spread evenly along the bottom ; the salt should be very finely 

 pulverized to prevent decrepitation. The boat with its con- 

 tents should, after weighing, be at once inserted into the tube 

 and the asbestos plug D which should have been highly heated 

 and still be hot, shoved in close behind the boat. 



The tube is now heated gradually beginning at the plug. 

 As the water in such salts is driven out, in great part, at a low 

 temperature the heating must be cautiously done and the air 

 current must not be too slow else water may condense in the 

 cold part of the tube back of the plug. When heating salts 

 containing sodium bicarbonate, the regulation of the air cur- 

 rent is the more difficult since the acid CO„ of the bicarbonate 



