RECENT PROGRESS IN PHYSICS. 405 



but in general a separate decomposing cell is i)referable, in whicli the 

 anode is of gold, &c., connected with a common Daniell's battery. 

 The Duke Max Von Leuchtenberg, whose laboratory for galvanic 

 gilding is not surpassed b)'' any other, (tlie Elkiugton's operate prin- 

 cipally with silver,) uses plates of iron and coke charged with 

 sulpliuric acid, and the sulphate of iron produced covers the expense of 

 maintaining the battery. — (Dingler's Journal, vol. U7, from Technolo- 

 giste, August, 1845.) These batteriesare only charged on Mondays, and 

 thenusedjwithoccasionaladditions, day and night until Saturday, being 

 employed at night to decompose the exhausted gold solutions, as gold 

 anodes are not employed, they being considered dead capital and a 

 temptation to the workmen. The gold solutions, are prepared in the 

 laboratory in the following manner : One part of gold is dissolved in 

 aqua regia and evaporated to dryness, a solution of one part of caustic 

 potassa is added, the mixture heated and then filtered. The Duke 

 considers those solutions best whicli contain per decilitre 1 to 0.25 

 grammes of gold. The extent of this establishment may be imagined 

 when we learn that (Dingler's Journal, vol. 105, from Bulletin's de 

 r Academic de St. Petersbourg, No. 130,) three wooden vessels lined 

 with India-rubber held 5,500 litres of gold solution containing about 

 80 pounds of gold, and that sometimes in one month GO pounds were 

 precipitated, as when 204 pairs of copper capitals and bases for St. 

 Isaac's church were gilded; the total weight of these was 7,200 " pud," 

 of 16 kilogrammes, and the surflice to be gilded was about 1,300 square 

 metres. During three j^ears 280 kilogrammes of gold were used ; eight 

 elements were usually employed as a single pair, but when the solu- 

 tions were nearly exhausted they were combined as a double-paired 

 battery, or the size of the anode was increased. If the current was 

 too strong, so that gas appeared at the kathode, or the object became 

 dark colored, the surface to be gilded was sometimes increased by 

 adding other objects. As soon as the precipitate appeared " matt,' 

 the articles were taken out and rubbed with the wire-brush, and this 

 was repeated three times in order to obtain a sufficient gilding. 



The application of magneto- electrical machines appears to offer con- 

 siderable advantages for o})erations on a large scale. It seems that 

 Sturgeon was the first to use them, but Woolrich first secured a patent 

 for their application to manufacturing purposes, which was afterwards 

 bought by the Elkingtons. — (Dingler's Journal, vol. 105, from Bul- 

 letin de St. Petersbourg, ISo. 130.) The latter had a machine con- 

 structed for their manui'actory of German silver ware, which daily 

 precipitated seven Russ'an pounds of silver. It consisted of eight 

 horse-shoe magnets, each of twelve steel plates, two and a half inches 

 wide, and together four inches thick. Their length from the pole to 

 the vertex of the arch was two and a half feet, and the arms were six 

 inches apart. The iron cores of the armatures were six inches long, 

 two and a half inches thick, and placed radially upon a wheel of two 

 and a half feet in diameter, towards which the magnets were also ra- 

 dially directed. The wheel made TOO revolutions in a minute, and the 

 current deposited sixteen to twenty ounces of silver in an hour.* 



[*The use of this machine has been discontinued, as it was not found as advantageoui 

 as was originally supposed. G. C. S.] 



