Scientific Intelligence — Chemistry and Mineralogy, 207 



polished cast-iron being connected with the negative pole and immersed in 

 the filtered solution. One pair of the plates had hardly sufficient inten- 

 sity for the purpose. The coating of silver speedily begins to be depo- 

 sited, and is sufficiently thick in half an hour. It is then polished by a 

 smooth surface of iron and subsequent friction with soft leather. There 

 seems little reason to doubt that the process might be applied, under 

 proper arrangements, to the coating and preserving of large objects of 

 cast-iron, such as statues, &c., exposed to the weather ; and by occa- 

 sional simple cleaning, such as is usually applied to plated objects, the 

 surface of the metal might be maintained with all the brilliancy of po- 

 lished silver. Mr Connell has also found that a solution in water of the 

 crystallised double cyanide of gold and potassium answers very well for 

 the galvanic gilding of silver. This salt is easily prepared by precipi- 

 tating a solution of gold in aqua regia by excess of ammonia ; and dis- 

 solving the well- washed and still moist fulminating gold in a warm so- 

 lution in water of a quantity of cyanide of potassium, equal in amount to 

 the gold which had been deposited in the aqua regia. By concentrat- 

 ing the solution, the double cyanide is obtained on cooling. With a mo- 

 derately strong solution of this salt, and a power of two pairs of Smee's 

 plates, small silver objects, such as salt-spoons, were readily gilded after 

 three-quarters of an hour's action. '^For larger objects, a more powerful 

 battery would probably be required. In this way the trouble of previ- 

 ously preparing the cyanide of gold is avoided, which substance, as is 

 well known, has been used for electric gilding, when dissolved in cyan- 

 ide or procyanide of potassium. 



11. Extraction of Palladium in Brazil. — The extraction of palladium 

 from the auriferous sand of Brazil consists in fusing it with silver, and, 

 consequently, forming a quaternary alloy of gold, palladium, silver, 

 and copper, which is granulated by projecting it into water. 



By treating this alloy with nitric acid, the gold is separated from the 

 other metals which are soluble in the acid ; the silver is precipitated by 

 a solution of common salt in the state of insoluble chloride, which being 

 separated, the copper and palladium are precipitated by plates of zinc. 

 The pulverulent deposit of these metals is re-dissolved in nitric acid, and 

 the solution precipitated by excess of ammonia, which re-dissolves the 

 oxide of copper and of palladium. When the ammoniacal solution of 

 these metals is saturated with hydrochloric acid, a double chloride of 

 palladium and ammonia is deposited in the state of a crystalline yellow 

 powder, and this, when calcined in a crucible, is readily decomposed, and 

 leaves spongy palladium.-;— PAi7osc>pAicai Magazine, vol. xxiii., No. 153, 

 p. 398. 



12. Wifhkritc, a New Mineral Species. — Under this name, given in 

 honour of Professor WOhler, Scheerer of Christiania has described in 

 Poggendorff's Annals a substance found on some islands of the Lange- 



