Glass Working Bifocals for the Undergraduate Laboratory Chemistry majors a t Rensselaer Polytechnic Institute, asked to prepare and characterize nonstoichiometric TiO,' are required to seal the substrate in quartz tubes under vacuum for reaction and heat treatment. Many of our students who wear eyeglasses experienced considerable difficulty with the usual clipon glassblower's glasses worn over their eyeglasses and then under a pair of safety goggles as required by our safety rules. In addition, regular glassblowing glasses give inadequate protection from the intense glare from the heated quartz. An interim solution was to attach appropriatelyshaped pieces of cobalt blue glass to special safety goggles provided for this step of the enperimeut.2 Although this solution permits comfortable viewing of the heated quartz, the cobalt blue glass is t w dark to give adequate vision for other manipulations necessary during the sealing procedure. The design presented here obviates this difficulty.
an omride
Instead of filling the entire visual field with the blue glass, only the bottom half of the goggles had glass pieces, suitably cut to fit, cemented onto the frame withan epoxy resin, producing "glass-working bifocals". With this "bifocal" design, one can easily switch viewing fields asappropriate to the task, without having toremove orreplace thesafety goggles continually as the work is heated and cooled. Further, it keeps the absorbing glass outside of the safety barrier. We have heen careful to maintain the integrity of the eye shield of the safety goggles by attaching the blue glass directly to the frame; the epoxy bead does not touch the flat plastic eye shield itself. We have not observed any deterioration of the plastic frame on any of several pairs using various brands of 5-min epoxies prepared according to manufacturen'directions. The attachment has remained firm for at least five years in some of our goggles, but because the frame is flexible, we recommend frequent inspection of the seal. The authors would like to thank Timothy Walsh for bringing his glass-cutting skills to bear upon this design.
' MCCarthY. G. J. J. Chem. Educ. 1972,49,209. The goggles described here have a flat face plate and are of the style known as a MonWgle, a product of American AllsafeCompany. Tonawanda. NY.
J. W. Zubrlck Hudson Valley Communily College Troy, NY 12180
R. A. Bailey Rensaelaer Polytechnic Institute Troy, NY 12181
Volume 65
Number 10
October 1988
919
