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. 



o o o 



Pface nnncfer each hole 



OOOO O O o 



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 tlie 

 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. 



