212 ANNUAL OF SCIENTIFIC DISCOVERY. 



moisture of the air ; and by this means the current very soon becomes too 

 weak. As Bunsen has found that the decomposition of the chlorides into 

 metal and chlorine depends especially upon the density of the current, par- 

 ticular attention was to be paid to the fulfillment of this condition. By the 

 employment, opposite to the great positive charcoal-pole, of a wire of the 

 thickness of a knitting-needle, the reduction of potassium, sodium, calcium, 

 strontium, etc., took place so easily that the author regards this experiment as 

 one that may hereafter be performed at lectures. It is, however, difficult to 

 obtain the separated metals in large globules. For this purpose the author 

 has suggested the three following methods : 



1. The employment of a platinum wire as the positive pole. By this means 

 the metal is aUoyed with the platinum. 



2. Two chlorides are melted together, in simple atomic proportions, to form 

 a fluid double chloride ; the temperature is regulated so that a solid crust is 

 only formed round the negative pole. On cooling, this is found filled with 

 metallic granules. 



3. The separation of the metal is affected immediately beneath the surface 

 of the fused chloride, by means of a pole composed of a pointed iron wire. 

 It remains protected by a thin stratum of the fused chloride, which covers it 

 like a varnish, and collects in masses of the size of a mustard-seed. 



Calcium. The method here first described is, it must be confessed, uncer- 

 tain in its results, but, in favorable cirurnstances, it furnishes globules of cal- 

 cium of the size of peas. A mixture of 2 equivalents of chloride of calcium 

 with 1 equivalent of chloride of strontium and muriate of ammonia is 

 melted in a Hessian crucible until the last-mentioned salt is volatilized ; a 

 cylinder of iron, serving as a positive pole, is then immersed in the fused mix- 

 ture, together with a narrow clay cell of the length of a finger, previously 

 heated to redness and filled with the same fused mixture ; this serves for the 

 reception of the negative pole, which consists of a piece of iron wire, or a 

 stick of charcoal of the thickness of a knitting-needle. "When the fused 

 chlorides in the clay cell stand froni -J an inch to 1 inch higher than hi the 

 crucible, the heat of the charcoal furnace may easily be regulated so that a 

 solid crust shall be formed only in the clay cell ; beneath this the separated 

 metal collects, without coming in contact with the clay cell. If the current 

 from 6 charcoal and zinc elements be then allowed to pass through for from 

 half an hour to an hour, a large quantity of reduced calcium is obtained. 

 But in general, by this process, the calcium is found in a pulverulent form dif- 

 fused through the mixture of chlorides, which violently decomposes water. 



The metal is obtained with more certainty, although in smaller fused glob- 

 ules, by putting the mixture into a small porcelain crucible, such as is used 

 for the calcination of precipitates, heating by charcoal or the spirit-lamp, and 

 passing the current through the mixture by a charcoal pole of as large size as 

 possible, and a piece of iron piano-forte wire (No. 6), not more than 2 lines in 

 length, which is united with the negative pole of the battery by means of a 

 stronger wire reaching close to the surface. A small crust is to be formed 

 round the wire at the surface. To collect the small globules deposited on the 

 wire, the latter must be taken out about every three minutes, together with 



