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To Tin Copper Tubes

W.

Wollweber recommends for still-worms copper tubes tinned inside in the following manner: To a solution of Rochelle salts a solution of salts of tin is added; a precipitate of stanfound thoroughly coated with zinc. Care must be taken not to leave the plates too long immersed in this bath, as its affinity for iron is such that they may become dissolved.

This is the case with thin plates of wroughtiron, which, even when 1/8 inch thick, may be dissolved in a few seconds. It is safe, therefore, to let the bath previously act on some wrought-iron, so that it dissolves a portion of it, in order to satisfy its inconveniently great affinity for this metal. 3650. To Zinc or Galvanize Grey Iron Castings. Cleanse the articles in an ordinary chating mill, which consists of a barrel revolving on its axis containing sand; when the sand is all removed, take them out and heat one by one, plunging, while hot, in a liquid composed as follows: 10 pounds hydronous tartrate is formed, which is washed and chloric acid, and suficient sheet zinc to make then dissolved in caustic lye. The copper a saturated solution. (See No. 3473.) In tube, which has first been rinsed with sul- making this solution, when the evolution of phuric acid and then washed, is then filled with the alkaline solution, warmed a little, and touched with a tin rod, which causes the deposition of a coat of metallic tin. gas has ceased, add muriate, or preferably sulphate of ammonia, 1 pound, and let it stand until dissolved. The castings should be so hot that when dipped into this solution, and instantly removed, they will immediately | ping, the articles of zinc are rubbed off thor dry, leaving the surface crystallized like oughly with finely-powdered pumice-stone frost-work on a window pane. Next plunge and rinsed in water, after which they are them while hot, but perfectly dry , into a bath placed in the bath and remain there for 24 of melted zinc, previously skimming the oxide hours. After that time they are again on the surface away, and throwing thereon a rinsed in water and simply wiped off. The small amount of powdered salammoniac. copper or brass covering has a very bright If the articles are very small , inclose them in look, as if polished, and adheres perfectly. a wrought-iron basket on a pole, and lower The thickness of the coat may be increased them into the metal. When this is done, afterwards by the aid of a battery. shake off the superfluous metal, and cast them into a vessel of water to prevent them from adhering when the zinc solidifies. 3651. To Zinc Copper or Brass Vessels. Boil the vessel in a solution of chloride of zinc, adding a quantity of zinc turnings to the solution. 3656. Dullo's Method of Platinizing Glass. This is recommended to prevent fusing of the thin end of a glass tube used for a blowpipe. In drawing out the end of the tube, leave the diameter slightly larger than is necessary; then roughen the narrow end with a file. chloride of platinum, containing 5 per cent. of Dip in a solution of biheat cautiously till the glass acquires a metallic appearance. Repeat this 4 or 5 times.

3657. Boettger's Method of Platiniz-

3652. Boettger's Process for Coating Copper and Brass with Zinc by a Wet the metal; remove excess of the drop, and Process. Place zinc in grains or powder in a non-metallic vessel, and cover the zinc with a concentrated solution of sal-ammoniac; warm to ebullition, and introduce into the ing Glass. Pour rosemary oil upon the dry mixture the objects of copper or of brass chloride of platinum in a porcelain dish, and which it is desired to coat, after having pro- knead it well until all parts are moistened; perly cleansed them. After a few minutes, then rub this up with 5 times its weight of the object will be covered with a brilliant, lavender oil, and leave the liquid a short time firmly adhering deposit of zinc. (See No.3312.) to clarify. The objects to be platinized are to