42S 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. [November 25,IS 71- 
quantity of paper, which, at one time, had a delicate 
yellow tint, due to yellow chromate of lead, hut which had 
been spoiled and changed to a dirty brown “by the 
gaseous emanations from the river water,” used as a 
source of power in the paper mills. But, perhaps, the 
most striking proof consists of a facsimile of a memoran¬ 
dum, written with water from the river Calder. The 
writing is the colour of faded ink, and runs thus:— 
“ Dedicated, without permission, to the Local Board of 
Health, Wakefield. This memorandum, written with 
water taken from the point of junction this day between 
the river Calder and the town sewer. Could the odour 
only accompany this sheet also, it would add much to 
the interest of this memorandum.” 
The report next deals with the West of England 
clothing districts; but, although the details as to the 
source and materials of pollution vary somewhat, the 
effects are substantially the same. Rivers and streams 
w r hich, if they were preserved in a state of purity at all 
approaching that in whioh they leave the fountain 
head, would be a source of health and wealth to all the 
towns through which they pass, are made utterly use¬ 
less and noxious to the general community. 
In dyeing the “ superfine black ” cloths of the West of 
England, the manufacturer depends on a basis of indigo 
colouring, or woading, as it is called. It is incidentally 
mentioned, that for the dyeing of other tints, the magni¬ 
ficent colours now manufactured from coal tar, and known 
ns aniline colours, are becoming gradually more employed 
in the place of various dye-woods. This, it is thought, 
will have some influence in diminishing the pollution of 
rivers, as it will reduce the amount of waste dye-woods 
which are generally cast into the nearest watercourse, 
and the residual liquids of the dye vats are of a less pol¬ 
luting character and more easily purified ; since, unlike 
the aqueous extracts of dye-woods, they contain but very 
little extraneous matter either in solution or suspension. 
(To be continued.) 
THE THEORY OF DISSOCIATION. 
computed from the heats of combustion. By the com¬ 
bination 
of 16 pts. of oxygen with iron, are evolved 66,100 thermal 
emits. 
„ „ hydrogen „ 59,200 „ 
so that the difference 
6900 
shows how much more heat is consumed when H 2 0 in¬ 
stead of H 2 is separated from the compound FeOH.,- 
Q, and consequently dp, is greater in the case of steam. 
Calling the pressure of the hydrogen p\ and that of the- 
steam p 2 , we see that p 2 increases faster than p v and that 
the ratio p 1 : p 2 diminishes as the temperature rises; and 
this is confirmed by experiment. 
If it be supposed that the quantity of heat which, 
during the process of decomposition, is consumed for 
internal work (this quantity, in the case of hydrogen, 
being called U, and in the case of iron IJ 2 ) docs not 
vary with the temperature, then another equation can 
be deduced— 
in which R = 
= C 
U_ 
AR 
1 
T 
760 
5 ° 2 7 a’ 
s 0 being the molecular volume of 
H 2 or of H 2 0, and U = U] — U 2 . The unknown quanti¬ 
ties C and U can be determined by two observations, 
and then the above equation will furnish the value of' 
~ for every temperature. 
The following table shows how far the experimental 
values agree with those obtained by calculation from, 
the equation:—■ 
mperature. 
Found. 
Calculated. 
200° 
20-49 
23-07 
265° 
13-96 
14-01 
363° 
8-62 
8-11 
440° 
5-75 
5-75 
860° 
2-34 
2-08 
1040° 
1-74 
1-65 
1600° 
0-92 
1-06 
BY A. HORSTMANX.* 
The author traces the connection between the tempe¬ 
rature, pressure, and the other elements which are of 
influence in a case of dissociation lately examined by H. 
Ft. Claire Deville. When steam acts upon iron in a 
closed vessel, there exists at every temperature a ten¬ 
dency towards the establishment of' a constant ratio be¬ 
tween the partial pressures of the steam and of the hy¬ 
drogen which, while dependent upon the temperature, 
appears to be independent of the quantity ©f iron and 
its oxide, and of the absolute pressure of the gases. This 
may be explained by Pfaundler’s hypothesis that in a 
given time there are as many molecules of water decom¬ 
posed as newly formed. The author considers it admis¬ 
sible to suppose that, at the moment when these two 
reactions take place, a molecular compound FeOH 2 is 
foraied, which, however, according to temperature or 
other circumstances, is immediately split up again either 
into Fe + H 2 0, or into FeO + H 2 . If such a compound 
were formed, then according to the mechanical theory of 
heat, the pressure of the hydrogen and that of the steam 
would increase according to the same law, which can be 
expressed by the equation— 
dp — d T 
AT So 
whore A represents the mechanical equivalent of heat, 
T the absolute temperature, 8v the volume of the libe¬ 
rated gas, Q the quantity of heat consumed in the pro¬ 
cess of decomposition, and dp the increment of pressure. 
P v remains the same for steam and hydrogen. Q, can be 
* Deutsch. Chem. Gesch. Ber., iv. 635, and Journal of the 
Chemical Society. 
The value of U is found from the above equation to be* 
— 3900 heat units instead of — 6900, which number- 
would directly follow from the known heats of combus¬ 
tion of hydrogen and iron. But considering the sources 
of error to w T hrch the determinations of the heats of com¬ 
bustion, as well as the ratioare subject, we must be- 
P2 
contented that the value of U, whether obtained directly 
or indirectly, has the same sign and is of the same order. 
Do Sunflowers follow the Sun ?—Many of the- 
statements which are demonstrated in the progress of 
science to be erroneous have, as a foundation, a sub¬ 
stratum of fact. The popular notion that the sunflower 
followfl the sun in its course has been often combated 
and contradicted, but, according to Mr. J. A. Allen, one- 
species at least of the genus Hclianthus has this pecu¬ 
liarity. He says, “ It is a popular belief that- the sun¬ 
flower always turns its flowers towards the sun, but in 
reality, so numerous are the exceptions to this rule in 
our garden sunflowers and in our common [American] 
wild species of the East, that few observing people 
regard it, doubtless, as otherwise than an idle whim. 
With many of the prairie sunflowers, however, the facts- 
are different; especially is this so in the case of Jt£. 
rigidus. Morning after morning, at flowering time, the 
heads of this species may be seen bending gently towards 
the east; they are erect at midday, and at evening* 
gracefully droop towards the west. This continues, day 
after day, for weeks, with surprising regularity and uni¬ 
formity ; later, however, the stems grow rigid, and re¬ 
main nearly vertical. In this case, at least, the popular 
notion referred to above seems well founded.”— Gardeners' 
Chronicle, 
