I. BATTERIES. 303 



1257a. Porty Cells of a Rod Chloride of Silver Battery ? 



being part of a battery of 8,040 cells. 



Warren De La Rue, F.R.S., and Hugo W. Muller, F.R.S. 



The elements consist of a flattened silver wire and a zinc (non-amalga- 

 mated) rod. The electrolytes are a solution of chloride of ammonium, 23 

 grammes to a litre of water, and fused chloride of silver cast on to the silver 

 wire. 



When the terminals are not connected, the battery is quite inactive ; one 

 such battery has been in action since November 1874. In order to prevent 

 contact between the chloride of silver and the zinc rod, the rod of chloride of 

 silver is encased in a tube of vegetable parchment open at both ends. The 

 cell is a glass tube closed with a paraffin stopper. 



Such a battery will evolve three cubic centimetres of mixed gases per 

 minute, if connected up with a voltameter containing one volume of sulphuric 

 acid, and eight volumes of water. 



This battery is particularly well suited to experiments with a large number 

 of elements, on account of its constancy. 



8040 cells give a spark in air between a point (positive) and a plate 

 (negative) of 0'342 inch (8 '68 mm.) ; the striking distance (distance explosi ve) 

 is shorter when the point is negative and the length of the spark is materially 

 affected by slight differences in the form of the point ; the point used is 

 parabolic in form and is made of copper wire 0*125 inch (3 '175 mm.) in 

 diameter, the plate 1*1 inch (27 "94 mm.) in diameter. The length of the 

 spark between a point and a plate appears to be in excess of the ratio of the 

 square of the number of cells ; for example 8,000 will give a spark 64 times 

 as long as the spark from 1,000 cells. Between two spherical surfaces of 

 3 inches (76 '2 mm.) radius and 1*5 inch (38*1 mm.) in diameter; the 

 striking distance (distance explosive) is only 0*038 inch (2'1 mm.) ; between 

 spherical surfaces the law of the striking distance being in the ratio of the 

 square of the number of cells does not hold. When a resistance is introduced 

 into the circuit of 6,000,000 Brit. Ass. units (ohms), a series of intermittent 

 brilliant sparks is obtained like those from an electrical machine ; but without 

 resistance when the spark jumps the ordinary voltaic arc is formed. The 

 current of 8,040 cells passes through a residual Irydrogen vacuum of 38 mm. 

 tension in a tube 1-6 inch (40*6 mm.) diameter, and 27 inches (58 '58 

 centimeters) between the terminals ; the current of 1,200 cells passes with a 

 tension of 2 mm. 



1258. Portable Medical Battery, with modified form of 

 De La Rue's chloride of silver and zinc elements. 



Tisley and Spiller. 



1259. New Galvanic Battery for Domestic Purposes. 



Aurel de Ratti, 



This Zinc-Carbon Battery is charged with a saturated solution of sulphate 

 of magnesia or Epsom salts, a very cheap material. The flask above the cell 

 is filled with crystals of this salt, on which a saturated solution of the same is 

 poured until the flask is quite full. The cork with the glass tube is then 

 forced down till the solution rises and fills the tube. A small cork is loosely 

 fixed in the open end of the glass tube. No air must be allowed to remain in 

 the tube or flask. The latter is now inverted, and the tube introduced through 

 the round hole in the lid. The flask will be held in position by the projecting 

 cork fitting into the round hole. The end of the glass tube will thus be im- 

 mersed in the solution in the jar. The carbon- plate is finally pushed through 



