Popular Science Monthly
��607
���Filtering Mercury
THE mercury used in a laboratory for ex- perimental p u r - J) OSes often picks up particles of grit or metal filings that can be most easily re- moved by filter- ing. This should be done under pres- sure.
Put the soiled mercury in a glass syringe tube. Closing the small end with the finger, insert a thin section of perforated cork, then some asbestos wool, and finally a perforated India- rubber cork. The asbestos should be sufficiently tight to prevent the mer- cury from passing at ordinary pressure. Tie on the cork with twine and invert over a suitable vessel. Then compress the air above the mercury by means of a cycle-pump, using only just enough pressure to drive the metal through the filtering material. It will come out clean and bright, leaving the impurities in the asbestos fibers.
As the wide end of a syringe tube has a distinct rim, there will be no difficulty in wiring the cork in position to avoid the possibility of its being forced out by the compressed air. — H. J. Gray.
A Simple Bit Gage
THE amatenr mechanicwho relies upon his sense of touch or "feel" to select a bit of the proper size, frequently makes the mistake of choosing the wrong size and thus drills a hole which may be too large or too small for his purpose. This source of error may he eliminated if a piece of sheet brass is perforated with a number of holes cor- responding in size with the bits in one's outfit. The sizes should be marked in the brass beneath each hole; and when a ])articular bit is wanted, the desired size can be determined by inserting the bit into its corresponding hole. By this method errors arc easily avoided.
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Pface nnncfer each hole
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����Blacking Box Inside Brush
AB L A C K - I N G box can be made, which is lodged inside the polish- ing brush. To this end the large and flat brush has a wood backing which is hollowed out at the middle for fitting in the black- ing box. A second wood piece of the same size as the brush backing is applied upon the latter and it is also hollowed in the center, so that the blacking box is contained in the cavity formed be- tween the two wood portions. The top Avood piece is held on in any suitable way which will allow it to be readily re- moved and replaced.
Razor Blade Floor-Scraper
AVERY service- able floor %^ e 'f'Tzl ' '"'"---^ scraper can ^' '-'^^-
be made very quickly from a piece of wood and an old plane iron. The handle should be shaped from hardwood to which the plane iron is fastened as shown. Be- sides using it on the floor it will be found very handy for scraping off old paint.
A Novel Polishing Pad
A\ERY use- ful and ef- ficient polishing pad may be eas- ily made with a small e m p t y spool, some cot- ton-wadding and a piece of flannel. Cut the flannel in a circular form
about eight inches in diameter, placing the cotton-wadding in the center, the outer portion of the flannel being drawn in and tied firmly to the center of the spool. \\ hen polishing operations are to be commenced, simply pour the polish through the whole in the center of the spool. — George H. Holuex.
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