Fune 11, 1885] 
is used to indicate the density of the liquid while the cells are 
being charged and discharged. Mr. Preece puts into his battery 
a charge of about 120 ampere-hours twice a week. Hourly 
measurements of E.M.F. current and density of liquid have 
enabled him to know the condition of his battery at any period 
of charge or discharge. These measurements have been plotted 
out into curves, the ordinates showing volts, amperes, and specific 
gravity, and the abscissze hourly observations. When each 
magnitude reaches its constant, bubbles of gas are freely given 
forth and energy is being wasted. The variation of the electro- 
motive force and current strength is clearly due to the counter- 
electromotive force of the cells, which becomes a’ maximum 
only when the plates are fully formed. The counter-electso- 
motive force partakes of the character of a higher resistance 
opposing the charging current, and increasing the proportion of 
the current through the shunt of the dynamo. Hence the 
changes of eleetromotive force are more marked than those of 
the current. Indeed, the changes in the electromotive force, as 
given by the voltmeter, are sufficient alone to indicate the pro- 
gress and completion of the charge. They are more reliable 
than the evolution of gas. 
The electrical leakage of Mr. Preece’s cells is obviated by 
standing each cell on three porcelain supports, having cups half 
filled with resin oil on Messrs. Johnson and Phillip’s plan. 
Mr. Preece gives the E.M.F. of the battery at its terminals 
as— 
When charging 2°25 per cell 
When idle... os 275 yy 
When discharging HATS en 
and the internal resistance per cell as— 
When charging ‘0060 ohm 
When discharging "OOly 43 
But the latter is said to vary very markedly within the strength 
of current of discharge. This is shown by the following experi- 
ment, made with 23 cells of a smaller type than those described 
above, which are used in the Post Office :— 
Current of discharge Internal resistence 
in amperes in ohms 
4°39 0°7608 
WES eee 0°4607 
15°84 0°2816 
25°07 0°1969 
Thinking that this remarkable diminution of internal resist- 
ance might be due tothe evolution of heat, Mr. Preece measured 
the temperature with a delicate thermometer. 
Normal temperature of cell 123° C. current of discharge :— 
5 amperes ... No alteration of temperature perceived 
10 op An exceedingly slight change 
16 aA About 123° 
20 4 Barely 13° 
The current in each case was kept on for twenty minutes, 
hence the diminution, Mr. Preece says, is not due to heat. 
Since the internal resistance varies in this way Mr. Preece 
now always takes the internal resistance with the same current, 
viz., IO amperes. 
The author of this paper asserts that the capacity of these 
batteries certainly improves with age, and up to the present 
time he has seen no sign of decay or deterioration. 
M. Plante informed him that, though in course of time the 
peroxidised plate becomes very brittle, it is impossible to per- 
oxidise it completely through ; there always remains a metallic 
core to give it strength. Mr. Preece finds that this is so. Up 
to the present moment he has made no careful measurements of 
the efficiency of his battery. He puts in about 240, and takes 
out about 200 ampere-hours weekly, and does not observe any 
change or fall in the electromotive force. When the electro- 
motive force of these cells falls, it falls rapidly, indeed almost 
suddenly. Occasionally one plate of a group becomes inactive 
from undue local action, or from bad connection (shown by the 
colour). This plate is removed and put in a ‘‘hospital” cell, 
where it is brought into order either by a greater density of 
current or by reversal. 
Reversing has a great beneficial action on a cell ; it not only 
improves its capacity, but it removes any cause of irregular 
working. It is advisable to do this periodically. Mr. Preece has 
two extra cells, which enables him to have two cells always } 
NATURE 
143 
under reversal by means of the charging current. It takes from 
1,000 to I,200 ampere-hours to reverse a cell, so that at this. 
time of year it takes a month or more to complete the operation, 
and it will take a year to reverse the whole battery. Sixteen 
cells have been reversed during the past twelve months. 
Chemical Society, May 21.—Dr. Hugo Miiller, F.R.S., 
President, in the chair.—Messrs, E. G. Amphlett and E. G. 
Hogg were formally admitted fellows of the Society.—The 
following papers were read:—A colorimetric method for deter- 
mining small quantities of iron, by Andrew Thomson, M.A, 
—On some sulphur compounds of calcium, by V. H. Veley. 
—Spectrosc spic observations on dissolved cobaltous chloride, by 
Dr. W. J. Russell, F.R.S. The characteristic absorption- 
spectrum given by cobaltous chloride after dissolution in such 
media as pure and dry potassium chloride, sodium chloride, 
calcium chloride, alcohol, glacial acetic acid and in chlorhydric 
acid, is seen also in an aqueous solution. Hydrated cobaltous 
chloride gives an entirely different spectrum. If a somewhat 
faint indication of the spectrum of the chloride be taken asa 
standard, it is found possible to determine with tolerable accu- 
racy when the amount of anhydrous chloride in solutions of 
varying strength and temperature is identical with that in the 
standard solution. A solution containing 4°18 grams of cobalt 
chloride in 10 c.c. of water at o° C., when observed through a 
thickness of 7 mm., forms a convenient standard. If to 1o ce. 
of such a solution 2'9 cc. of water be added, then on raising the 
temperature to 33° an amount of anhydrous chloride is re-formed 
identical with that existing in the standard solution at o°: this 
rise of temperature exactly counteracts the effect of adding 2°9 
cc. of water. A series of determinations were made in this 
manner, and it was found that the number of c.c. of water 
added to the Io cc. of standard being as given in the upper 
line, the temperature at which the spectrum appeared was as 
given in the lower line in the table :— 
43° 
16'0 
95° 
Again, taking the most dilute solution, in which 16 cc. of 
water had been added to to c.c. of the standard solution, it was 
found that the same change was effected—z.e. that the chloride 
spectrum could be developed in it, by the addition to the solu- 
15‘0 
‘tion of either 0°864 gram of hydrogen chloride gas, or 5°26 of 
sulphuric acid, or 2°47 of calcium chloride ; but that the addition 
of sodium chloride would not develop the bands, although on 
heating the solution after saturating it with this salt a tempera- 
ture of 34°5° was sufficient, instead of 95°, to develop the bands. 
Zinc chloride was found to act in a different manner. Notwith- 
standing its power of combining with water, on adding it to the 
cobalt solution no banded spectrum shows itself, and even when 
added to a solution in which the spectrum is visible it causes 
its disappearance. The explanation is that it must have com- 
bined with cobalt chloride, forming a new and stable compound. 
On evaporating the solution this was found to be the case, and a 
new salt, a compound of cobalt and zine, crystallised out. Cobalt 
bromide, both as a solid and in solution, gives a spectrum very 
similar to that given by the chloride, but the corresponding 
bands are nearer the red end of the spectrum. The salt is far 
more soluble in water than the chloride, and has a stronger 
affinity for water, as is shown by the much higher temperature 
required to neutralise the power with which water combines 
with it. The following determinations similar to those made 
with the chloride show the increase of temperature necessary to 
counteract the combining power of giving quantities of water 
with cobalt bromide :— 
Standard + Water Temp. 
IO ¢.c. One. 
TOo 0 ae ee nO 51 
MY on ar Zi 57 
UO A ar ya! gt 
—The sulphides of titanium, by Prof. T. E. Thorpe, F.R.S.— 
Note on the formation of titanous chloride, by Prof. T. E. Thorpe, 
F.R.S. 
Zoological Society, June 2.—Prof. W. H. Flower, 
V.P.R.S., President in the chair. Mr. Sclater exhibited draw- 
ings of and made remarks upon the specimens of various species 
