44 
SOME PRINCIPLES AND METHODS OP POCK ANALYSIS. [mn.L.l7G. 
current of air continues to pass the gradual heating and subsequent 
f usion'of the flux is brought about by the blast-fed sliding ring-burner 
R'" (tigs. 8 and 9). The sodium-tungstate joint is shielded from the 
flame by small pieces of asbestos board P (fig. 9), cut out so as to fit 
the crucible. When fusion is complete, as shown in the case of sodium- 
carbonate flux by the decided slackening of the gas current through 
the safety bulbs attached to the drying tube, the flame is extinguished 
and a current of air is allowed to continue until the apparatus is cold. 
This apparatus suffers from the drawback of being slightly permeable 
Fig. 9. — Arrangement during fusion of Gooch apparatus for determining water. R'", blast-fed rin 
burner; P, protective asbestos-board shield resting on ring R"; FF, board forming end of frame an 
covered with asbestos board to prevent being set on fire by the heat of the blast. This serves at th 
same time as an efficient shield for the absorption-tube A. In it there is bored a round hole at hi 
through which passes the outlet tube from the crucible. B, sulphuric-acid bulbs serving to sho 
the rate of gas current through the absorption-tube and at the same time to prevent back entry < 
moisture from the air into A. 
to combustion gases at high temperature. The defect can be overcom 
by causing the flame to play upon an outer ordinary platinum crucibh 
kept permanently filled with sodium-potassium carbonate. This pre 
tective crucible, however, is soon ruined for other purposes, bein 
distorted by the alternate expansion and contraction of the carbonate 
It has been found that if the operation is carried out expeditious] 
and the final full heat applied for but a few minutes the error due 1 
penetrating water gases is inappreciable. This hastening m&y be re 
dered safer by using rather finely powdered calcium chloride in t\\ 
