558 CHEMISTBY. 



of nickel contain six and not seven atoms of water. At a temperature of 5'P — 

 68° F., he obtained rhombic crystals with 7 H 0, at 86° — 104° F., quadratic 

 crystals with 6 H 0, and at 122° — 158° F., monoclinonietric crystals with 6 H 0. 

 These remain transparent above 104° F. ; at ordinary temperatures, they gradu- 

 ally become opaque, without loss of weight. Dimorphism, therefore, exists in 

 the salt with 6 H 0, but not in that with 7 H 0. 



From solutions of sulphate of magnesia at 158 c F. of sulphate of zinc at 131- 

 F., and of sulphate of cobalt at 122° F., he obtained compounds analogous in 

 composition, and isomorphooa with the above mentioned monocliuometric crystals. 

 Ch. G. 329. 



Silver. — Deville finds that silver is rapidly dissolved by hydriodic acid with 

 evolution of hydrogen, especially if heat be applied ; the iodide separates in luge 

 hexagonal prisms ; palladium is also attacked, but slowly. Gold and platinum 

 do not evolve any sensible amount of hydrogen, but are gradually dissolved, 

 while all the common metals are dissolved with remarkable energy by hydriodic 

 acid. Deville is inclined to class silver with mercury or even with lead. 



Sexqui-Salts of Manganese. — Cariue prepares the anhydrous sulphate of the 

 sesquioxide, by forming an artificial brown oxide, by passing chlorine through a 

 solution of carbonate of soda, in which rmito-carbonate of maDganese is suspended. 

 This, wheu dry, is triturated with sulphuric acid into a thin paste. The mixture 

 being heated in an oil bath, oxygen is evolved, but at 230° F., the evolution 

 stop?, and a violet gray mass is produced. At 270° the green sulphate is formed. 

 It can be washed with nitric acid, and heated to 266° to drive off excess, and is 

 then pure. It is very easily decomposable, and can only be kept in closed tubes. 

 By absorption of water, hydrated sesquioxide is produced. It is not soluble in 

 diluted sulphuric acid, unless some of the proto-salt be present, wheu it readily 

 dissolves, forming a red solution. 



Antimony. — Rose meutions some experiments by Weber to determine the 

 atomic weight of antimony, the terchloride was pre ;ipitated by sulphuretted 

 hydrogen, and the chlorine determined as usual ; uuless tartaric acid be used, a 

 little chlorine remains with the sulphide. In this way, the number 1608.67 was 

 obtained, agreeing closely with that of Schneider, viz., 1503. Rose adds that 

 many years ago he determined the atomic weight from the two chlorides, and 

 found 1513.14 and 1508.5. 



Non-precipitation of Metals. — Martin has made some experiments on the in- 

 fluence of strong hydrochloric acid in preventing the precipitation of metals by 

 sulphuretted hydrogen. LeaJ, cadmium, antimony, tin, mercury, bismuth, copper, 

 and silver, are not wholly precipitated unless a large quantity of water be em- 

 ployed Lead requires the smallest quantity of acid to retain it in solution, and 

 the other metals in larger quantity, in the above order. The portion of the 

 chlorides of copper, mercury, and bismuth, which remains dissolved, is converted 

 into sub-chloride. 



Arsenic Acid. — E. Kopp having prepared large quantities of this substance as 

 a substitute for tartaric acid in the discharge style of calico-printing, was led to 

 examine the different hydrates. As O 5 + 4 aq. separates from the gently evapo- 

 rated solution in large crystals, heated to 202° P., a creamy substance, consisting 

 of little needles, is formed, which is the terhydrate, As 0'' + 3 aq. If the solution 

 be heated up to 284° or 356° F., rectangular prisms are formed, they are 



