NOTES AND QUERIESby@scientificamerican


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(1) H. P. says: Please inform me of some recipe for removing superfluous hair. A. Make a strong solution of sulphuret of barium into a paste with powdered starch. Apply immediately after being mixed and allow to remain for ten or fifteen minutes. See also p. 107 (8), vol. 38, and p. 25, current volume. (2) M. A. C. writes: I would like to know how to dissolve bleached shellac, to make it a cement for stone. A. Dissolve it by digestion in 3 or 4 parts of strong alcohol, or by the aid of ¼ its weight of borax in about 4 volumes of boiling water. (3) A. K. asks: 1. In rating substances as to hardness, diamond being No. 10, how do aluminum, osmium, iridium and steel as used in steel pens, number, also common and tempered glass? A. Aluminum about 3, iridosmine 6.5 to 7, steel 5.5 to 6, glass 5 to 5.5. 2. Can glass 1/32 inch in thickness be ground to angles of 15 per cent or less, and points as fine as pins, without difficulty, and how? A. No. (4) D. C. S., asks for a good recipe for cleaning and polishing dirty and tarnished brass. A. Dip for a short time in strong hot aqueous solution of caustic alkali, rinse in water, dip for a few moments in nitric acid diluted with an equal volume of water, rinse again, and finish with whiting. (5) C. J. H. asks for the simplest way of producing a coating of the magnetic or black oxide of iron on iron plates 3 feet x 6 feet. I think it is called the Barff process. A. See pp. 1041 Scientific American Supplement, and 232, vol. 36, and 4, vol. 37, of the Scientific American. How can I make tissue paper impervious to air and water, and yet strong enough to confine gas? A. You may pass the fabric through a solution of about 1 part caoutchouc in 35 parts of carbonic disulphide, exposing it then to the air until the solvent has evaporated.
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