36 S. L. Penfield — Methods, for Determination of Water. 



eter is drawn out like fig. 7. The end is rounded and flared 

 out a little. Two clylinders of platinum are next adjusted, 

 one on the inside the other on the outside. These are made 

 from pieces of platinum foil, about -07 mm in thickness and 



7. 



: i6c.M. :_ ..I 1 ?.**-,,. __j i 6 .C;M-. ! 



8xll cm in diameter, which have previously been bent around 

 glass tubes of such a size that when applied to the combustion 

 tubing the spring of the metal will hold them in place. A 

 large platinum boat, 7 to 8 cm long and 11 to 12 mm in diameter 

 with a cross section like fig. 8, should be used, since this will 

 s. readily hold a gram of mineral mixed with 5 



grams of sodium carbonate. Sodium carbonate 

 dried at near its fusing point is not very hygro- 

 scopic. Thus 2 - 5 grams of it, spread out on a 

 watch glass gained only '0002 grams in 15 minutes. 

 After the boat containing the mixture has been shoved within 

 the platinum casing, the tube is connected with a suitable dry- 

 ing and absorption apparatus and heated in the furnace which 

 is constructed like fig. 6 except that only three bricks are used. 

 The tube is placed in the angle formed by the charcoal lining, 

 some pieces of charcoal are placed at the sides in front, leav- 

 ing an opening through which the flame may be directed, and 

 an additional piece is laid on top. The tube can readily be 

 brought to a full white heat, and hy forcing a slow current of 

 dry air through the apparatus the carbon-dioxide resulting 

 from the decomposition can be removed, and the water carried 

 over into the weighed absorption tube. The glass fuses be- 

 tween the platinum casings, and in a number of experiments 

 that have been tried there has not been a single instance where 

 the glass tube has broken or shown any indication of leaking. 

 After heating, the tube will not crack if it is left to cool 

 slowly on the charcoal, but it cannot be used a second time as 

 it will be very apt to break where the platinum is fused on to 

 the glass. At the high temperature to which the glass is sub- 

 jected, it of course becomes very soft and the ends must be 

 properly supported, also the rubber connections and absorption 

 apparatus must be carefully screened by asbestus board. By 

 constructing a cover for the boat no material need be lost by 

 spattering, and after making the water determination the con- 

 tents may be used for the remainder of the analysis. With 

 some samples of topaz that were experimented upon, the escap- 

 ing carbon-dioxide carried off traces of the mineral and sodium 



