X S E W NETHOD F O R D E T E R M I S I S G 'I'XPORDEKSITIES BY PHILIP RLACKM-kN
PART VII' -4 wide tube is closed a t one end A, and the open end is drawn out to a nozzle B, just wide enough t o allow a small glass-stoppered weighing-bottle t o pass through it. A permanent line is marked on the tube some distance away from the closed end and the volume of the tube D from -4 to the mark is determined once for always marked permanently on the A arid the value glass. -4piece of rubber pressure-tubing, sex:eral metres long, has one end C closed with a clip or pinchcock, and the other end fitted with a glass tube D about I metre in length. The tube D is kept upright, and dry, clean mercurjr is poured in until both rubber tube and D are filled; both are agitated t o remove all air-bubbles. The weighed quantity (a)of substance to be experimented on is introduced into the measuringtube *IB,the end C of the rubber tube fastened onto B, placed x-ertically with -1to the top, D fixed high up in an upright position, the pinchcock or clip opened and the mercury in ,1B brought to the mark by raising or lowering D, Fig I. the difference jm,) in height between the mercury levels measured, -ABsurrounded by a suitable heating-jacket and heated in the vapor of some substance boiling well above the temperature a t which the substance experimented on vaporizes a t 7 6 0 mm pressure, and D further raised (or else mercury poured into it) to maintain the mercury in AB (11)
Continued from Jour. Phys. Chem , Berlin, 41, 441 (1908).
12,
692 (1908); Ber. chem. Ges.
434
Philip Blackma?%
at the mark. The difference ( m 2 ) in height between the mercury levels is now ascertained, the external temperature (t,) and pressure (p) determined, and the necessary calculation effected by means of the formula
the temperature of the heating medium). It must be remembered that the volume of the weighing bottle should be subtracted from ?I before proceeding with the calculation of the result. This apparatus may not be found as simple or convenient to manipulate as those described in Part T-I, but it possesses these advantages over those detailed in Parts I-IT7 (Journal of Physical Chemistry, 12, 679 688 (1908)): ( I ) the determinations are always carried out a t constant volume ; and ( 2 ) the measuring tube AB can be made as small as one pleases, thus reducing the combined dimensions of the measuring-tube and heating-jacket to a small compass. (For instance, for a permanent measuring capacity of 50 cc, the combination need not occupy a bulk more than 30 cm by 4 cm). Some difficulty may be encountered in fixing, raising, and lowering D, on account of the fairly considerable length of C D ; but a piece of string fastened to D and passed over some form of support fixed high up should quite easily facilitate the matter. The measuring of 771, and vz, ma>- also present some little inconvenience for the same reason ; generally however ?x, will not exceed 80 cm, and if w be a moderately small quantity wz2 will rarely be greater than 2 metres. (t,
=
PART VIIIl The simple equation giyen on page 689 (Journal of Physical Chemistry, 1 2 (1908)) can be derived from the two equations given on page 688 (Ibid.) as here shown. On page 688 let wl, w2,throughout be replaced by x,, x 2 , respectively, and the equations then become C f . Ber. chem. Ges. Berlin,
41, '4s;
(190s)
-YewMethod
joy
Determining Vafior-deizsz‘ties.
435
+
and w = x, x,. As x, = w - x,, the first equation can be written
-
d2x1
d,(w - x,) =
d,d?\rj(fi?
+
1%)(273 3’068 ( 2 7 3
t l > -l’l(pl 1- t d ( 2 7 3
- 1’2,)(273 -~ t?)]
+ t?)
Let this last equation be multiplied right through by the quantity IOO w ,and the result is
+
1 0_0 d , . d~ ( i ~ (hf i 7~7 ?_2 )_ (2i3 ____ ~ _ 11) _ -_ 31068u(273
+ ~711)(273+ t ? > l
--1(p,
+ f1)(273 + f?)
But IOOZ, %J is the percentage composition of one component, and IOO - IOOX, w is that of the other constituent; if these quantities be respectively w i t t e n as wl, xi2, the equation takes the form d+,
+ (I,( 100 - kL) I O O d l ~ ( 2 [ i 2 ( f i 2& 7112)(273 - _______
- fl)-Z,(fi,
~~
31068a(273 - fl)(273
- ”21)(273
+ t?)
->;)].
Corrigenda Page 6S0, line 26; instead of
“pl
=
p ? ” read ‘*p1=
P?).” Page 680, line 2 9 ; instead of ‘ ( a ? , volume” read “z12 volume. Page 687, line 2 1 ; instead of ‘‘*A and i j ) ” read “-4, and (j).” Page 688, line 4 ; instead of ”
Page 690, line 3 0 ; instead of “ninth, and eleventh” read ‘‘ and ninth. ’ ’ Page 7 2 5 , line 13; instead of “ 6 5 1 ” read ‘‘661.” H n c k u c ) Trclz ii zcal I u A t i t u t c , Loiidolz, E , E)zSlun(i
