CHEMICAL SCIENCE. 219 



JELECTEO-PLATIXG WITH THE WHITE METALS. 



Aluminum and Silicium obtained from Clay, Stone, and Sand. In the An- 

 nual of Scientific Discovery for 1855, pp. 235, 236, some account was given of the 

 experiments of Dr. G-ore, of Birmingham, England, whereby he was enabled 

 to effect an electro-piate of the white metals aluminum and siliciurn, from the 

 compounds of their oxyds, clay, sand, etc. As this subject is one of no little 

 importance, we give in the following article the experiments of Dr. Gore some- 

 what in detail. 



To coat articles of copper, brass, or German silver with aluminum, take 

 equal measures of sulphuric acid and water, or take one measure each of sul- 

 phuric and hydrochloric acids, and two measures of water ; add to the water 

 a small quantity of pipe-clay, in the proportion of five or ten grams by weight 

 to every ounce by measure of water (or one half ounce to the pint), rub the 

 clay with the water until the two are perfectly mixed, then add the acid to 

 the clay solution, and boil the mixture in a covered glass vessel one hour. 

 Allow the liquid to settle, take the clear supernatant solution, while hot, and 

 immerse in it an earthen porous cell, containing a mixture of one measure of 

 sulphuric acid and ten measures of water, together with a rod or plate of 

 amalgamated zinc ; take a small Smee's battery, of three or four pairs of plates, 

 connected together intensity fashion, and connect its positive pole by a wire 

 with the piece of zinc in the porous cell. Having perfectly cleaned the sur- 

 face of the article to be coated, connect it by a wire to the negative pole of 

 the battery, and immerse it in the hot clay solution ; immediately abundance 

 of gas will be evolved from the whole of the immersed surface of the article, 

 and in a few minutes, if the size of 'the article is adapted to the quantity of the 

 current of electricity passing through it, a fine white deposit of aluminum 

 will appear all over its surface. It may "then be taken out, washed quickly in 

 clean water, and wiped dry and polished ; but if a thicker coating is required, 

 it must be taken out when the deposit becomes dull in appearance, washed, 

 dried, polished, and reimmersed ; and this must be repeated at intervals, as 

 often as it becomes dull, until the required thickness is obtained. "With small 

 articles it is not absolutely necessary, either hi this or the following process, 

 that a separate battery be employed, as the article to be coated may be con- 

 nected by a wire with the piece of zinc hi the porous cell, and immersed in 

 the outer liquid, when it will receive a deposit, but more slowly than when a 

 battery is employed. 



To coat articles with silicium, take the following proportions : three quar- 

 ters of an ounce, by measure, of hydrofluoric acid, a quarter of an ounce of 

 hydrochloric acid, and forty or fifty grains either of precipitated silica, or of 

 fine white sand (the former dissolves most freely), and boil the whole to- 

 gether a few minutes, until no more silica is dissolved. Use this solution 

 exactly in the same manner as the clay solution, and a fine, white deposit of 

 metallic silicium will be obtained, provided the size of the article is adapted 

 to the quantity of the electric current. Common red sand, or indeed any 

 kind of silicious stone, finely powdered, may be used in place of the whito 



