107. COMPOSITION OF VARIOUS ALLOYS.--Brass is composed of two parts of copper to one of zinc; or copper and calamine, (an ore of zinc,) equal quantities. Pinchbeck consists of from five to ten parts copper, and one of zinc. Bell metal is composed of three parts copper and one of tin. Gun metal, nine parts copper and one of tin. Tombac, sixteen parts copper, one part zinc and one of tin. The composition of pewter is seven pounds of tin, one of lead, four ounces of copper and two of zinc. That of type-metal is nine parts lead, two parts antimony and one of bismuth. Solder, two parts of lead with one of tin. Queen's metal, nine parts of tin, one of bismuth, one of antimony and one of lead. Jewel gold is composed of twenty-five parts gold, four parts silver, and seven parts fine copper. In forming metallic compounds or alloys, it is proper to melt such of the ingredients as are the least fusible first, and afterwards add the others, stirring them briskly till they are thoroughly commixed. 108. TO PRODUCE VARIOUS KINDS OF GAS.--To three or four ounces of pulverized chalk or marble, moistened in a flask, with an equal quantity of water, add one ounce of sulphuric acid;--carbonic acid gas will be evolved in abundance, and will rise through the neck of the flask, and may be conducted by pipes, to any proper receiver. Instead of the marble or chalk, substitute granulated zinc;--in this case hydrogen gas will be evolved; but this may require a larger proportion of water. Pour sulphuric acid upon a similar quantity of dry muriate of soda;--muriatic acid gas will be rapidly evolved. Proceed in the same manner with a similar quantity of black oxide of manganese,--apply the heat of a lamp, and oxygen gas will be produced. Put into the flask, two or three ounces of lean beef, cut into small pieces; pour over them one ounce of nitric acid diluted with three ounces of water; apply the heat of a lamp, and nitrogen gas will be liberated. Powder separately, equal quantities of muriate of ammonia and newly burnt lime; put them together into a flask and apply gentle heat; ammoniacal gas will be evolved. Pour an ounce of nitric acid, diluted with five times its weight of water, upon one ounce of shreds or turnings of copper; nitrous gas will be rapidly evolved. Grind three parts of muriate of soda with two parts of black oxide of manganese; introduce this mixture into the flask, and add two parts of sulphuric acid, diluted with an equal quantity of water; apply a gentle heat and chlorine gas will be evolved. _Note._--When either of the last mentioned gases are produced, great caution is requisite that they do not escape into the room, in any considerable quantity, as their action on the lungs is exceedingly injurious.