CHEMICAL SCIENCE. 177 



bring the ore to a semi-liquid paste. The presence of different salts, 

 especially sea-salt, assists the reduction of the chloride of silver, but the 

 carbonate of lime hinders it. 



In nearly all the processes of amalgamation, the first operation con- 

 sists in changing to a chloride the sulphuret of silver, after which the 

 chloride must be reduced, so that a considerable portion of the mercury 

 is lost. This, with other considerations, prompted the authors to search 

 for a process by which the sulphuret of silver might be directly reduced 

 without changing it into a chloride. The reagent which they consider 

 the most effective is metallic copper used at the temperature of boiling 

 water, and associated with certain salts, sulphates of copper, iron, or 

 alum. A process newly introduced, which dissolves the chloride of sil- 

 ver into a concentrated solution of sea-salt, offers many advantages, 

 among others the avoiding the use of the costly reagent mercury, and 

 if there are no practical difficulties in the way, the general employment 

 of this method would cause a large increase in the production of silver. 



METALS IN SEA-WATER. 



IN continuation of the researches mentioned above, Messrs. Malaguti 

 and Durocher, in company with M. Sarzeaud, have made a series of ex- 

 periments to discover if silver and other metals occur in sea-water. 

 Water taken some leagues off the coast of St. Malo was found to con- 

 tain a little more than 100.500.000 of silver, while the ashes of the fucoidal 

 plants serralus and ceramoides contained i^cco- They have also detect- 

 ed silver in sea-salt, in common hydrochloric acid, and in the soda of 

 commerce, as well as in the rock-salt of Lorraine. Pursuing their in- 

 vestigations, they have obtained such indications as leave no doubt of the 

 existence of silver in vegetable tissues and in the blood of cattle. In 

 the ashes of pit-coal, silver has not been clearly detected. Although 

 lead and copper have not been directly detected in sea-water, the exist- 

 ence of about T.oilo.ooa f lead a d a small quantity of copper in the ashes 

 of various species of Fucus has been clearly established. 



POISONOUS EFFECTS OF ZINC. 



IT is now some time since it was proposed by M. Leclaire of Paris to 

 use oxide of zinc as a substitute for white lead, with a view to avoiding 

 the dangerous effects of the latter on the workmen. There could be 

 little doubt that, in point of salubrity, oxide of zinc was an improve- 

 ment on carbonate of lead ; but it was still a matter worth determining 

 to what extent the oxjde of zinc was itself free from objection, and 

 whether or not some precautions were necessary regarding its use. 

 M. Flandin endeavoured to determine this experimentally. He rubbed 

 animals over with ointment of oxide of zinc, of carbonate of lead, and 

 sulphate of lead ; and whilst he found that the two last always pro- 

 duced poisonous effects, he observed that the animals rubbed over with 

 oxide of zinc continued to enjoy their usual health. Cases have, how- 

 ever, occurred, which show that the innocuousness of oxide of zinc 



