214
JOURNAL OF CHEMICAL EDUCATION
'
FEBRUARY, 1932
then immediately resmoked. It is next slowly cooled in the hot air above the burner, and finally wrapped in cotton for complete cooling. The process consumes considerable time, and troubles beset the novice a t every step. The hot glass may sag out of shape while his attention is given to adjusting the burner; the brush flame may soften the glass enough to cause collapse; careless or hasty manipulation above the burner in the cooling stage may cause strains to develop that will defeat the purpose of the entire operation; and finally the hot glass may set the cotton afire with the almost certain destruction of the finished piece. Most of these dangers can be avoided by providmg two extra burners for the heating operations, and replacing the cotton wrapping with a cooling tray filled with asbestos fiber. A Fisher burner is very good for the general heating, and a Tinil burner with a wing top for the smoking. The former should be adjusted to a yellow flame for working soft glass and to its maximum temperature for pyrex. Gas for the Tirril may be enriched with gasoline as described above. The cooling trays are made of sheet metal cut in the shape shown in Figure 6 and with the sides turned up along the dotted lines. A sheet of asbestos is placed in the bottom and covered with a quantity of asbestos fiber. The U-shaped notches accommodate pieces longer than the tray. Annealing pyrex glass is sometimes omitted altogether, but the beginner will lind the general heating of a joint advisable though smoking and wrapping are unnecessary. Liteiature Cited HOSHALL, "Apparatus for Supplying Air Snder Pressure," J. Cmnr E ~ u ,c7, 2674 (1) (Nov., 1930). Goggles -. for precision glass blowink Assuring maximum protection and comfort for the eyes, while a t the same time offering perfect observation of the incandescent are an important work in or out of the flame, the Burgess-Parr glass blower's goggles ~contribution toward precision glass blowing. The new goggles are based on the use of a special didymium glass which possesses the unique characteristic of transmitting all light except thr ubjectiunable yellow glare from incandescent glass. The pink~shlcnscs arc mountcd in a newly de5igned bakelitr lrnmr which provides comfort, eliminates the transmission of heat t o face and ean, and is strictly non-inflammable. ,Also, the lenses are adequately protected against accidental breakage. Although the lenses appear surprisingly transparent to most light, they are nevertheless completely opaque to the particular glare of incandescent sodium glass, thereby entirely eliminating the only serious and bothersome light encountered in working glass. The transparency t o other light makes it entirely practicable t o wear thegogglesindefinitely, since they do not materially interfere with normal vision when looking for objects on the work bench or elsewhere. When observing a piece of glass in the flame, one sees only the red glow of the glass. Not only are the eyes greatly relieved, but far more accurate work is possible since the exact outline of the glass can be seen a t all times, Much time is also saved. The goggles are also suitable in cyanide case hardening, eliminating the terrific glare. ~
