Penfield and Bradley — Precipitates on Asbestos. 453 



Art. XLII. — Filter Tubes for Collection of Precipitates 

 on Asbestos; by S. L. Penfield and W. M. Bradley. 



The tubes described in this article may be employed to 

 advantage in a variety of analytical operations, and as an inex- 

 pensive substitute for a Gooch crucible, where a high tem- 

 perature is not required. 



The tubes (figure 1) may readily be drawn out from com- 

 bustion tubing, or made from soft glass if high temperatures 





are not used. Different lengths and sizes will find a variety of 

 uses, and diameters from 17 to 20 mm may be recommended for 

 general use. The most satisfactory support for asbestos is a 

 perforated platinum disc 0*2 mm in thickness, to the center of 

 which a platinum wire three inches long is soldered (figure 2). 

 "Where conditions or expense prohibit the use of platinum, a 

 fitter bed of quartz may be substituted with excellent results. 



