1854.] 



ON THE ELECTRO-PLATINa OF METALLIC ARTICLES. 



15 



days later than usual ; the Lilac was in bloom on the 5th of May, 11 

 days earlier than usual; and Strawberries were ripe on the 14th of 

 June, one day earlier than usual. — London Times. 



E. J. LOWE. 



On tlic Clectro- Plating of Metallic Articles with White 

 lUetalsi) Aiuminium and Siliciiini^ from Clay^ Stone) and Sand« 



By G. Gobe, M.D. 



It has long been known to chemists that aU kinds of clay, stone, and 

 sand, of which the crust of the earth is composed, consist of metals com- 

 bined with oxygen, carbonic acid, sulphuric acid, and other non-metallic 

 elements, forming therewith oxides, carbonates, sulphates, &c. ; thus 

 clay is an oxide of aluminium, sand an oxide of silicium, limestone a 

 carbonate of the oxide of calcium. But the separation of the metallic 

 bases from the non-metallic elements with which they are combined, 

 has been a matter of so great a difficulty, that but few chemists have 

 put themselves to the trouble of accomplishing it, and those who have 

 done so have made use of the most powerful means and reducing 

 agents, such as large voltaic batteries, potassium, &c., and have then 

 obtained them in a state of alloy or combination with mercury. Sir 

 Humphrey Davy, the discoverer of most of these bases, in his experi- 

 ments on the decomposition of the alkalies and earths, used a power- 

 ful battery, consisting of 500 pairs of plates, and then succeeded in 

 obtaining ( hem combined with mercury, from which they were afterwards 

 separated ; Wohler and Berzelius, in their discoveries of the means of 

 separating the metals aluminium and silicium from their respective 

 compounds, clay and sand, used a high temperature and potassium, 

 and then, succeeded in obtaining them in the condition of dull metallic 

 powders, nearly invisible. 



By a means recently discovered, and described in the March 

 number of the " Philosophical Magazine" for this year, I have suc- 

 ceeded in depositing the metals aluminium from clay, and silicium 

 from sand stone, each in a perfect metallic condition, by dissolving 

 pipe-clay, common red sand, pounded stone, &c., in various chemical 

 liquids, and passing currents of electricity from ordinary small voltaic 

 batteries through the solutions. 



My attention has since been directed to produce simple processes, 

 whereby any person not possessing a knowledge of chemistry may 

 readily coat articles with those metals, and caus^the discovery to be 

 immediately applied to human benefit in the arts and manufactures, 

 and the following are the results of my experiments : — 



To coat articles of copper, brass, or German silver, with aluminium, 

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

 each of sulphuric 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 gi'ains by weight to every ounce by measure of water (or 

 i oz. 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, wliile hot, and immerse in it 

 an eartliern porous cell, containing a mixture of one measure of sul- 

 phuric acid and ton measures of water, together with a rod or plate of 

 amalgamated zinc ; take a small Smee's batter}-, of tlu'ee 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 surface of the article to be coated, connect it 

 by a wire with the negative pole of tlic battery, and immerse it in the 

 hot clay solution ; immediately abundance of gas will be evolved from 

 the whole of the immersed surface of tlie article, and in a few minutes, 

 if the size of the article is adapted to the quantitj' of the current of 

 electricity passing through it, a fine white deposit of aluminium will 

 appear all over its surface. It may then be taken out, waslied quickly 

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

 is required, it must be taken out when tlio deposit becomes dull in ap- 

 pearance, washed, dried, polished, and re-immcrsed ; and tliis must 

 be repeated at intervals, as often as it becomes dull, imtil the required 

 thickness is obtained. With small articles it is not absolutely 

 necessary, either in this or the following process, that a separate bat- 

 tery be employed, as the article to be coated may be connected by a 

 wire with the piece of zinc in 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 follovring proportions : 

 three-quarters of .an ounce, by measure, of hydrofluoric acid, a quarter 

 of an ounce of hj'drochloric acid, and forty or fifty grains either pre- 

 cipitated silica or of fine white sand, (the former dissolves most 

 freely), and boil the whole together a few minutes, until no more 

 silica is disolved. Use the 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 white sand, 

 and ivith equal succees, if it be previously boiled in hydrochloric acid, 

 to remove the red oxide of iron or other impurities. 



Both in depositing aluminium and silicium, it is necessary to well 

 saturate the acids with the solid ingredients by boiling, otherwise 

 very little deposit of metal will bo obtained. 



Among the many experiments I have made upon this subject, the 

 f jllomng 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 po- 

 rous cell, containing dilute sulphuric acid and apiece of amalgamated 

 zinc ; immersed a similar piece of bright sheet copper in the alkaline 

 liquid, and connected it mth the negative pole of a small Smee's bat- 

 tery 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 aluminium. 



Experiment 2. Obtained from a railway cutting in the town, a 

 small piece of the sand rock upon which Birmingham is built, boiled 

 it in hydrochloric acid, to remove the red oxide of iron, waslicd it clean 

 with water, and dissolved it by boiling in a mixture of hyilro-fluoric 

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

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

 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 1\ parts of carbo- 

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

 gas ceased, and a perfect glass was formed i poured out tlie melted 

 glass, and when cold dissolved it in water and used tliis solutiom 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 Birming- 

 ham are macadamised, 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 mixture of J oz., 

 by measure, of h3-dro-fluoric acid, J oz., of water, and \ oz. each of 

 nitric and hydro-chloric acids, until no more would dissolve ; used the 

 clear portion of this solution in the same manner as the former li- 

 quids, and readily coated in it a piece of brass with a beautifully wliito 

 deposit either of aluminium 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 pur- 

 chase of the poorer classes articles of taste and cleanliness which arc 

 at present only to be obtained by the comparatively wealthy. 



The following specimens accompany the communication, and may 

 be seen at the society's house ; — 



1 St. One specimen each of sheet copper and brass, coated with alumin- 

 ium from " I'ipe-cluy," according to process dcscribcJ. 



2nd. One specimen each of sheet copper and bra-ss, coated wiUi 

 silicium, from silica and sand, according to proce,**:} described. 



3rd. Specimen of Birmingham sand rock. 



4th. Specimen of ditto, purified by hj'dro-chloric acid. 



5th. Specimen of shoot motal coated with silicium from Birming- 

 ham sand-stone. 



