The sun., 1900-12-30


sugar and has prepared many new va
rleties; and IL appears lkcly that the ter
penes, a class OF bodies allied TO turpen-
tine, and comprising most of the substances
10 which tho odor OF flowers Is due. may
thereby find their explanation. 1t may
he mentioned In passing that Pasteur.
having found that ordinary mould de-
stroyed one variety OF tartaic acid rather
than the other In u mixture Of the two.
and made use OF this observation In order
to prepare the unattached variety in
state of purity, was led to study the action
Of organisms more or less resembling
mould. and that this has led to the devei-
opment Of the science of bactcriology,
which has had on enormous influence on
our views regarding fermentation in gem
eral. and guides the work of our physi-
clans. our surgeons witness Listers anti
septic treatmentl. our sanitary engineers
In their estimate OF the purity Of drinking
water and OF the disposal of sewage, OF our
manufactures OF beer and spirits. Of wine
growers, and more recently OF farmers.
All these processes depend upon the action
OF organisms In producing chemical
changes, whether in the tissues Of the body.
causing or curing disease. or In the pro-
duction Of favored alcohol from sugar.
or In the manufacture OF butter and cheese.
or in preparing the land for the recep-
ton OF crops We also owe 10
the genius OF Want HoG the most
important advance Of recent times
in the region Of physical chemistry. 1t
had been observed by NJ Raoult. pro-
fessor at Grenoble, that the freezing point
Of solvent Us general rule Is lowered
to the same extent II there be dissolved
in IL quantities Of substances propor-
tional TO their molecular weights. Thus
supposing $50 grams Of grape sugar be
dissolved in 100 grams Of water and the
solution cooled below o. c. with constant
stirring. ice separates suddenly in thin
spicules. and the temperature rises to
-o.ls5'. II S,42 grams Of cane sugar be
similarly dissolved in 100 grams of water
the freezing point Of the solution Is again
--Ols5'. Now $50 and 342 are respoc-
lively the hundredh part OF the molecular
weights Of grape sugar (Cs Hn Od and
cane sugar. Ga H9, On. Similarly. Raou!t
found that quantities proportional to
molecular weights dissolved in Il solvent
depress the vapor pressure Of that solvent
equally. or. what comes 70 the same thing.
raise its boiling point by an equal number
OF degrees. But ordinary salts. such as
sodium chloride, potassium nitrate, &c.
dissolved in water. give too great de-
preston Of the freezing point and too high
boiling point. Next. it had been OBJ
served by botanists. De Vries. PfeiYer and
others. who had examined the ascent OF
sap in plants. that II a vessel Of unglazed
porcelain, so treated as TO cause film OF
cupric ferrocyanide IA slimy red COM
pound TO deposit In the pores Of its walls,
be filed with a weak about per cent?
solution Of sugar or similar substance,
and plunged in vessel Of pure water.
water entered through the pores. BY
attaching manometer TO the porous vessel
the pressure exer,ed by the entering water
could be measured. Such pressure was
termed -osmouo pressure referring 10
the "osmosis' or passage through the
walls Of the vessel Such prepared walls
are perrneable freely TO water but not
to sugar OF similar bodies Want Hon
pointed out that the total pressure regis
tered Is proportional TO the amount OF
substance In solution. and that 1t IL pro-
porional to the absolute temperature,
and he showed. besides. tha. the pressure
eXeted by the sugar molecules is the Same
as that which would be exerted at the same
temperature were an equal number Of
molecules Of hydrogen TO occupy the same
volume as til" sugar solution. This
may be expr scd 10y stating that
when In dilute solution sugar molecules be-
have ds II they were present in the gaseous
state Here. again. however, il was noticed
that salts tended 10 give higher pressure:
Il was difficult to construct semi -permea-
BILE diaphragm. however. which would
resist the passage Of salt molecules. while
allowing those " water 10 pass freely.
Lastly. ArThenius Of Stockholm had shown
that the conductivity OF salt solutions
for electricity may be explained on the
assumption that when salt. such rs
KNO,. ia dissolved In water il associates
into portions similar in number and kind
TO those 1t would yield II electrolyzed and
II no secondary reactions were TO take
place.. Such portions TX and NOs for
e1ample) had been named ions by Faradsy.
Tho conductivity OF such solutions becomes
greater, per unit Of dissolved salt. the
Is reached, after which further diluton
no longer increases conductivity Now
Want Hoff united all these isolated OBJ
servatotl, and showed their bearing on
each other. Stated shortly. the hypothe-
sis is as follows: When n substance is
dissolved In large quantity Of a solvent.
its molecules ore separated from each
other to distance comparable with that
which obtains In cases. They are. there
fore oapab Of Independent action: and
when placed in vessel the walls Of which
are permeable TO the solvent. but not to the
dissolved substance t"seh.I-permeable
membrane - the imprisoned molecules
Of the latter exert pressure on the interior
surface Of these walls as II they were gas
eous. Want IIof showed the intimate
connection between this phenomenon and
the depression 81 freezing point and
vapor pressure already alluded to. lie
pointed out further that the exceptions
to this behavior. noticed In the case Of
dissolved salts. are due 20 their electric
"i,,{1,,inn u 20