The Western Union Telegraph Co. subjects its wires to the following test in order to ascertain that they are well galvanized. The wire is plunged into a saturated solution of sulphate of copper (blue vitriol), and permitted to remain in this for one minute, after which it is wiped clean. This process is repeated four times. If the wire appears black after the fourth immersion, it shows that the zinc has not all been removed, and that the galvanizing has been well done; but if it has a copper color, the iron is exposed, showing that the zinc coating is too thin. 0. G.
This simple test to determine the purity of white lead may be found useful where much painting is being done. It is as follows: Select a piece of charcoal of firm structure. and hollow out a cavity in one side about ½ inch in diameter and of the same depth. Put a sample of white lead in the hollow about the size of a pea, and subject it for a few moments to a blow-pipe flame. If the sample is pure, it will quickly reduce to metallic lead. Adulterated white lead will generally contain a residue that cannot be reduced. M. E. Canek.
To prepare packing for joints in pipes. etc., carrying gasoline vapor, mix a quantity of graphite and kerosene to a thick paste and apply the paste to both sides of sheet asbestos. When dry the packing may be cut to the shape desired. The graphite helps the asbestos make intimate contact with the iron and thus maintain a tight joint continuously at high temperature for an indefinite time. H. J. Bachmann.
For packing pumps on gasoline engines use asbestos wick-packing rubbed full of regular laundry soap; it will work without undue friction and will pack tightly. Common rubber-packing is not as good, as the gasoline cuts it out. A. A.
To cleanse mercury first put a ten per cent solution of nitric acid in an iron ladle, and then the mercury to be cleaned; place same over a blacksmith's forge until the nitric acid boils. The dirt will then rise to the top, and leave the mercury perfectly clean in the bottom. Care must be used not to let the mercury boil, as the fumes are very poisonous. H. C.
Some manufacturers make their belts and leather heavier in the following way: The leather is kept in a current of steam at low temperature until its pores are well open. Then it is put in a solution of glucose. The leather absorbs the liquid, and in drying the water evaporates and the pores close, retaining the glucose. To find out whether belts or leather have undergone this operation, put a piece of the suspected leather in some distilled water, and when it is well soaked, half fill a glass tube with some of the water, add a few drops of sulphate of copper, and fill the tube with a solution of caustic potash. Stir the liquid well and let it boil on an alcohol lamp. If the leather is natural, no change will take place in the liquid, but if it contains glucose, a characteristic precipitate of copper will form, due to the action of the glucose on the solution of sulphate of copper and potash. J. M. Menegus.
Los Angeles, Cal.