Page:Popular Science Monthly Volume 91.djvu/654

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��Popular Science Monthly

��is desired, it is best to proceed as follows: Apply a first plate and finish it. Then go over the operation again, dipping in the hot potash solution, rinsing, scouring, dipping again in the cyanide solution and replacing in the plating bath and then finishing and polishing a second time. This will give better results than if a very heavy plate were put on in one operation.

Articles of different metals or alloy, will not plate at the same time. This will be noticed if there is a soldered joint in the work. Such joints must receive treatment so the solder of the joint will take the plate as well as the rest of the surface. To plate on a soldered joint, make an ounce or two of saturated solution of sulphate of copper and distilled water. Add one-tenth of its volume of sulphuric acid. After the work has received the final scouring and rinsing, and before dipping in the cyanide bath, take a piece of small, clean, iron wire, or a small brush made of iron wire, and dip it in the sulphate solution and draw along the joint. A film of copper will cover the solder instan- taneously and to this the silver will readily adhere.

If the current is too heavy, the silver film deposited will lie loosely, with a hard dark appearance, and such a plate will not polish. This condition may be remedied by moving the articles farther from the anode and by raising the anode so that less of its surface is in the bath. Too high voltage with too little amperage will also cause a deposit of this kind. Articles being plated should be kept in gentle motion or moved frequently, as the solution has a tendency to settle, re- sulting in uneven plating.

Too much cyanide in the plating bath will cause the anode plate to assume a white frosted appearance with rough edges. A deposit from such a bath cannot be polished readily. Too little cyanide will cause the anode plate to be covered with a dark deposit having a hard, close-grained appearance, and the plating will be dirty and uneven. When either condition ap- pears, it should be remedied by the addi- tion of a small amount of silver solution, or of the cyanide solution, whichever is necessary. When a bath works properly and the anode remains clean and bright, the only material to be added is a little distilled water occasionally, to counteract evapora- tion. A plating bath will remain fresh for a long time if the evaporation is taken care of,

��and the vessel protected from dust and strong light.

All operations connected with the actual depositing of the plate and the first finishing should be conducted in dim light. A strong bright light will have a harmful effect on. both the plating solution and the freshly deposited silver.

��A Simple Toy Motor Run with Dry Sand

THE only materials needed in the con- struction of this sand motor are 2 needles, 1 cork stopper, some cardboard and heavy paper, glue and a quantity of fine sand.

The stopper should be a very large size. On both ends of the cork mark off with a pencil a 6-sided polygon. With a sharp knife cut the cork as shown in Fig. 1.

Cut six pieces of cardboard for the blades of the sandwheel and glue them to the cork as shown in Fig. 2. Push a needle, eye first, into each end of the cork, as shown.

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The sand falling from the cone drops on the edge of the uppermost blade of the wheel

The framework of the motor shown in Fig. 3 is made from three pieces of card- board glued together. The sand wheel is mounted at the bottom of the frame by pushing the needles through the cardboard. From the top of the frame a paper horn, filled with sand, is suspended by a short piece of thread. The sand sifts down over the blades of the wheel through a hole in the end of the horn. A small cardboard box should be placed under the wheel to catch the sand as it drops from the blades. A small grooved pulley wheel may be attached to one needle end and used with a thread for a belt to turn a light toy machine. The wheel can be fastened with a bit of wax. The sharp ends of the needles should be broken off. — E. P. Thornton.

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