The Molecular Volumes of Salt-Solutions. 



179 



into a battery which, requires no filling, and upon which tem- 

 perature and moisture are without influence. 



Since the resistance of the elements is a matter of indiffer- 

 ence, they may be made very small. I have filled glass tubes, 

 8 centim. long and 5 millim. diameter, half with the copper- 

 sulphate plaster and half with the zinc-sulphate plaster, wires 

 of copper and zinc being placed in the corresponding mixture, 

 which wires were then soldered together, as shown in the 

 accompanying figure. The ends of the tubes are closed with 

 paraffin. 



Twelve such elements form a row. 

 Twelve such rows stand one behind 

 the other, each connected with the 

 preceding one by insulated binding- 

 screws, so that each cbain of twelve 

 elements hangs between two binding- 

 screws. Any desired number of such 

 series of twelve elements may there- 

 fore be taken to produce the charge. 

 The whole battery of 144 elements 

 shows a polar difference of potential 

 of 152 volts ; whereas the same difference requires 156 ele- 

 ments of the freshly prepared water-battery and 200 of the 

 enfeebled one. The whole dry battery covers a surface of 

 16 centim. square. 



Postscript. — In the elements last prepared the zinc wires 

 are amalgamated at the ends and covered elsewhere with 

 shellac, and the concentrated solutions have been diluted with 

 one third of water. 



XXIV. The Molecular Volumes of Salt- Solutions. — Part II. 

 Water of Crystallization. By W. W. J. NlCOL, M.A., B.Sc, 

 F.R.S.E., F. C.S.j Lecturer on Chemistry, Mason College, 

 Birmingham* '. 



IN my previous paper f on this subject I showed that the 

 molecular volumes in solution of the metals sodium and 

 potassium, and those of certain acid-radicals — 01, (S0 4 ), 

 (N0 3 ), (CIO3), and (OH) — are constant in whatever way 

 these may be combined together to form salts, the essential 

 point to be observed being that the solutions are sufficiently 



* Communicated by the Author. 



t Phil. Mag. August 1883 ; Ber. der dent. Chem. Ges, xvii. p. 492. 



N2 



