SELECTION OF TECHNIQUES 



59 



Table 5-1. Standard Dimensions for Full-length Interchangeable Taper-ground Joints 



Computed 



Approxi- Diameter at 



Standard Approximate mate Length Large End of 



Joint Size Diameter at of Ground Ground Zone 



Number (^ Small End Zone (Gaging Point) 



Designation) mm. mm. mm. 



7/25 5 25 7.5 



10/30 7 30 10.0 



12/30 9.5 30 12.5 



14/35 11 35 14.5 



19/38 15 38 18.8 



24/40 20 40 24.0 



29/42 25 42 29.2 



34/45 30 45 34.5 



40/50 35 50 40.0 



45/50 40 50 45.0 



50/50 45 50 50.0 



55/50 50 50 55.0 



60/50 55 50 60.0 



71/60 65 60 71.0 



103/60 97 60 103.0 



Prepared by Kontes Glass Company from National Bureau of Standards Cir- 

 culars. Used with permission. 



Most glass apparatus made in the laboratory is formed from Pyrex 

 tubing or rod. Handling this glass requires a hot flame; usually a gas- 

 oxygen torch is used. With a little practice, almost anyone can make 

 simple items, and most laboratory biologists eventually become quite 

 proficient. Sheets for the construction of parts of an apparatus can be 

 cut from ordinary window glass. For very small animal or plant cham- 

 bers, or for situations where optical properties are important, windows 

 can be made from microscope slides or from the glass of 2 by 2 in. or 

 3V4 by 4 in. projection slides. Sheet Pyrex with good optical qualities 

 is available and can be fused into all-glass apparatus, usually a job for 

 a professional glass blower. 



If we re-examine the information in this chapter we find a good deal 

 of what could be called common sense. The selection of techniques or 

 instruments, as well as the assembly of parts, becomes easier with experi- 



