220 ANNUAL OF SCIENTIFIC DISCOVEKY. 



sand, and with equal success, if it be previously boiled in hydrochloric acid 

 to remove the red oxyd of iron, or other impurities. 



Both in depositing aluminum and silicium, it is necessary to well saturate 

 the acids with the solid ingredients by boiling, otherwise very little deposit 

 of metal will be obtained. 



Among the many experiments I have made upon the subject, the follow- 

 ing are a few of the most interesting: Experiment 1. Boiled some pipe- 

 clay in caustic potash and water; poured the clear part of the solution 

 into a glass vessel, and immersed in it a small earthen porous cell containing 

 dilute sulphuric acid and a piece of amalgamated zinc ; immersed a similar piece 

 of bright sheet copper in the alkaline liquid, and connected it with the neg- 

 ative pole of a small Smee's battery of three pairs of plates ; connected the 

 zinc plate with the positive pole, and let the whole stand undisturbed all 

 night. On examining it next morning, I found the piece of copper coated 

 with a white silver-like deposit of metallic aluminum. Experiment 2. Boiled 

 a mass of red sand rock in hydrochloric acid to remove the red oxyd of iron, 

 washed it clean with water, and dissolved it by boiling in a mixture of hy- 

 drofluoric acid, nitric acid, and water; immersed in this solution a porous cell 

 with dilute acid and zinc, as before ; connected a piece of brass to the zino 

 by a wire, and suspended it in the outer liquid, which was kept hot by 

 means of a small spirit lamp beneath. After allowing the action to proceed 

 several hours, I found the piece of brass beautifully coated with white metallic 

 silicium. Experiment 3. Took one part, by weight, of the same sand-stone, 

 after being purified by the hydrochloric acid, and 21 parts of carbonate of 

 potash, fused them together in a crucible until all evolution of gas ceased, 

 and a perfect glass was formed ; poured out the melted glass, and when cold, 

 dissolved it in water ; used this solution in the same manner as the former 

 ones ; allowing the action to proceed about twelve hours, when a good white 

 deposit of metallic silicium was obtained. Experiment 4. Took some stones 

 with which the streets of Birmingham are Macademized ; pounded them fine 

 in a mortar ; boiled the powder in hydrochloric acid, to purify it from iron ; 

 washed it well in water, and dissolved it by boiling an excess of it in a mix- 

 ture of f oz., by measure, of hydrofluoric acid, -J oz. of this solution in the 

 same manner as the former liquids, and readily coated in it a piece of brass 

 with a beautifully white deposit either of aluminum or silicium. 



From these and many other experiments which I have tried, it is quite 

 clear that common metal articles may be readily coated with white metals, 

 possessing similar characters to silver, from solutions of the most common 

 and abundant materials, and thus bring within the purchase of the poorer 

 classes articles of taste and cleanliness, which are at present only to be ob- 

 tained by the comparatively wealthy. 



BRASS FORMED BY GALVAISTIC AGENCY. 



Copper is more electro-negative than zinc, and separates more easily from 

 its solution than a metal less negative. If, then, in order to obtain a deposit 

 of brass by galvanic means, we employ a solution containing the two com- 



