THE ABSORPTION OF WATER AND DEUTERIUM OXIDE BY CELLULOSE
Experimental l'ethod
The vapour to be adsorbed is
in a tube V surrounded by a constant température bath. The amount adsorbed on the cellulose samples C is measured by observing with a cathetometer the extension of the quartz balances in the three tubes B, ,Bj,Bj, immersed in a thermostar. Trie tubes cont- aining the samples are evacuated through a liquid air trap T, by the bya-the mercury diffusion^xxpx pump D.P. backed by a Hy-Vac pump, the pressure in the apparatus being measured on the manometers M ,M(, or on the Mcleod guage Mc.l
Dry gases can be admitted through the liquid air trap or the P2O5 tube.
The mercury thermo-regulator R, is a slightly modified type containing three prongs to combine minimum lenght with maximum volume and yet ensure quick establishment of equilibrium owing to the large surface-volume ratio of the mercury bulb. The xsxiaixx régulâtor’is made out of Pyrex glass tubing, this is to do away xxik as far as poss ible with the effects of dilitation of the tubing of the regulator (Pyrex coef. dil. smaller than glass.) The regulator has a stopcock on a side tube by which the regulator may be used over a large range of températures, by adding or removing mercury through this tube. The capillary used is of the standard dimensions for regulators. The heating
System that the regulator opérâtes consists of an electric light bulb (100 7/atts) and one Cenco spoon heater, giving satisfactory results. The relay used was a Cenco polarizd -ed relay, but an ordinary Telegrpphjglay also has been used. o
The regulator maintains thebf the bath constant for several days to within 0.01 A
Balances
The balances were constructed after McBain and Bakr. They are fromrç quartz fibre maximum diameter 0.2mm., these fibres are from four to six feet long. The fibres were made by pulling rapidly in the oxy-acetylene flame quartz tubing 0.4 cm. in diameter.
The spiral is made by turning the fibre on a carbon rod (d:12mm.), while heating at the point of contact with a small hot flame. The spirals were made automatically with a spécial apparatus. This demands considérable practice and technic. The spiral
once made hâve to be tested for Hooke's Law. They are calibrated over the working range with a known weight anàthe deflection plotted against weighx, in ail three cases the
curve obtained was a straight line passing through the origin.
The spirals were placed in BI^B1,BJ, fumished with ground glass joints, they wBBe suspendedfrom small hooks in the top of the ground joints. These tubes arc conected to the rest of the system through the P2O5 tube. The cellulose was attached to the^spir
al by a hook.
Sensitivity of balances
The three spirals employed showed a deflection of 1mm. when supporting weights of 0.0056g. 0.0059, 0.0087g. respectivly. Thus with the cathetometer employed (reading to 0.01mm $ a weight of 0.00006g. could be detected.
Z
Z''
Procedure
The cellulose used was "Standard Cellulose" 99.5 a-cellulose, as prepared by the I.P.Co. The cellilose was placed on a hook, atrached to the spiral and ail put into tne tubes B ,B , B , .The ground joints were well lubricated and the caps set in place.
To supply water vapour to the apparatus a tube was placed at V containing the water, this water had been freed of ail dissolved gases by freezing and evacuating several times, until no différence was noted on the Mc.heod guage. This process was also used for DO.
The cellulose was dried by évaporation in tne presence of PgO^ from 12 to 24 hburs, after this time the reading is taken which corresponds to the dry weight.
The vapour pressure of the water was obtained by the indirect method that is, by surr- ounding the tube V with a vacuum flask and using compounds of a définite raelting point. The different agents used for this purpose are marked on the tables under the heading of agent.
The vapour pressures corresponding to the djfferent températures were obtained from the "Critical Tables". The bath was kept constant at 23.4 Cby means of the thermostatic control.
' Results The are in good that is why
izing details, but we note , as the température of the bath is raised, what we beleiveto be the condensation part of the curve occurs at a higher V.P. which one could well expect.
We hâve already made a run witn Dp0 but noticed a leak produce at 15°C,iîCk ----repeating this run to see
other than of D90. "le and Ètudy slowly but eratures, 1
température is raised the adsorption equilibrium takes longer perhaps this is due to the fact that the vapour pressure corresponds to that at which condensation sets in. Condensation is a much slower process. May I note here that we did not study the kinetics of H^O because it has already been done at various températures and the shape of the curve agréés with that of D 0.
In ail the measurements we take the leadings of three balances and take the averagê value. In kinetic studies the rate is so rapid we can only follow one balance during the run.
The lenght of time for equilibrium was 24 hours in general, certain authors hâve given two to three hours claiming that the adsorption has taken place after that it is condensation. Filby noted différences sometimes after several hours, but in our case the weight
used less and in general there was no différence after 12 hourâ.
We intend to study the results obtained*. and also those of D£Oof' which we on now, this will be done at a little later date.
adsorption of water vapour has been studied by several Researchers and our results agreement with theirs. The only means of comparison is to give the results in / R.v.l? one of the curves has been given in this manner We hâve not found any
revolution-Le a run vzitn ü ü but noticed a leak produce at 15
C,
zmx we are wether the cellulose has any marked différences toward D O than HO, could be expected due to the increaseddx density and other physical pro^erties made some kinetic curves of DgO at various températures, to see if we could follow the reaction, we noticed that after five minutes the absorption seems to take place regularilÿ, these curves show that equilibrium is reached verry rapidly at low temp- and after five minutes there is practically no measurable deflection, but as theof cellulose are working
Readings
The reading were made with the cathetometer, taking as the fixed jaina point a glass rod which was also suspended from the hook of the cap, this did away with any error due to the displacement of the cathetometer or the spirals between two successive readings
DgO used
Prepared bysNorsk Hydro Elektrisk Kvaelstotaktieselskab properties:
dxd :1.1049
TABLE FOR ADSORFTION KINETIC CURVES OF D2O AT VARIOUS TEMPERATURES
We followed the kinetics of adsorption on balance No.2
KINETICS at 0°C.
Position of central rod: 42.82 mm. Weight of cellulose corresp. to 0/o : 19.44+11.10
1 ... 23.30 ... 0.26 Minutes Hook % D90 0 ... 23.39mm. ...
..
o z : 30.54mm. défi. 3 ... 23.25 ... .. 0.42 4 ... 23.24 ... .. 0.45 5 ... 23.24 ... .. 0.45 6 ... 23.23 ... .. 0.49 7 ... 23.22 ... .. 0.52 8 ... 23.22 ... ... 0.52 9 ... 23.21 ... ... 0.55 .0 ... . 23.20 ... .... 0.58 AT 5.3°C KINETICSPosition of central rod: 42.70 Weight of
Minutes Hook
£
o
o 22.86 ... O2 2 rod:42.79 22.86 ... 0.29 5 ... 22.83 ... 0.38 10 ... 22.82 ... 0.42 20 rod: 42.76 22.78 ... 0.42 30 ... 22.78 ... 0.425
TABLE FOR KINETIC CURVES OF D2O
KINETICS ax 10.4°C
Fosition of central rod : 43.05mm. Weight
Minutes Hook _mm. 0 23.00 2 22.90 5 22.85 12 ... 22.81 21 22.79 40 22.76 60 22.75 80 22.74
of cellulose corresp. to 0^ :31.15mm. défi.
0 0.32 0.48 0.609 0.674 0.788 0.803 0.835
1 1 O \
iq rr\\T\ui<t5
cx^SO'tbhox û| Q 5«d° 'TirvU ’i-t\ Tï\lu
oi
ADSORPTION FOR BALANCE No.l Deflection for dry weight; 1668min. fc———--- — Time hrs. o
Tl
c Rod mm. Top hook mm. deflection mm. Agent % water on sam;: le Vapour pressure mm. o j.
iig. ï 2 solid 16.68 0 “'^2^ et h er 1 3 -27 28.75 6.79 0.15 CCL„ 4 0.89 . 0.389 5 -6.4 28.40 6.11 0.48 o-niti'o toi- 2.87 2.672 ene 94 0 28.46 6.03 0.57 ice 3.41 4.579 24 5.3 28.23 5.63 0.79 benzene 4.73 6.681 24 15.4 27.92 4.94 1.17 acetic ac. 7.01 13.12 18 18.1 27.46 429 1.36 Thermostat 8.05 15.58 46 19.5 27.51 4.04 1.66 thermostat 9.95 16.999 ‘ 32 1 20.1 27.65 4.09 1.75 Thermostat 10.31 17.64?
ADSORPTION FOR BALANCE No.7, Deflection for dry weight: 13.98 mm. Lme ars. oï
1
rod mm» Top Hook mm. deflection mm. Agent /ô water on sample R.v.P. in System solid !0 ðe 13.98 0 ? 3 -27 36.83 17.83 0.12 ccl4
0.85 1.80 /5 -6.4 36.29 17.02 0.39 o-nitro toi- 2.78 12.38 4 0 36.27 16.91 0.48 ene ice 3.43 21.22 ,4 5.3 36.10 16.57 0.65 benzene 4.64 31.17 ‘4r
15.4 35.54 15.69 0.97 acetic ac. 6.93 60.80 8 18.1 35.76 15.75 1.13 Thermostat 8.07 72.17 6 19.5 35.68 15.52 1.27 Thermo st aat 9.08 78.77 2 20.1 35.53 15.27 1.38 Thermostat 9.87 81.76/-7
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J 23-4° /’ 2oK /3 /6 o xï-> /o e 05 ÿ d « S-s. 7 6 O 4 3 2 / O iU 4 r'° /6 K 70 8o/3,
ADSORPTIÛN FOR BALANCE No.l Deflection for dry weight; 31.93 ram ?ime
rrs. Tl
0 C Rod mm. Ton hook mm. Deflectionmm. Agent on simpleD?0 V.F. Hpû
OX sol id 31.92 o C09 " eth( A/ 5T 4 - 25 21.81 3.76 0.32 CCL 1.003 0.476 4 3 - 7.5 21.74 3.11 0.90 o-nitro tolu 2.819 2.429 ene 18 0 21.63 2.69 121 ice 3.79 4.579 24 ->> 5.3 21.47 2.28 1.46 benzene 4.574: 6.681 24 13.2 20.74 0.87 2.14 6.70.4 11.379 24 15.2 20.43 0.36 2.34 7. .3.31 12.953 24 18.2 22.00 1.42 2.85 8.9 S 15.673 14 18.9 22.05 1.33 2.99 9.367 16.374 48 20 22.10 1.15 3.22 10.09 17.535 24 21.3 22.16 0.65 3.78 11.84 18.996 24 22.4 23.12 0.80 4.59 14.38 20.316 24 23.5 23.96 0.51 5.72 17.92 21.714
S'f-ADSORPTION OF DgO BALANCE No.2 deflection for dry weight; 29.75 mm. .me
1rs. °CTl Rod ram. Top hook
mm. deflectionmm Agent on seralDle/° N„o V.p. h
2
o-2 solid • • • • • • • • 29.75 0 l ;o9& ether 4 4 -25 43.35 23.38 0.22 ccl
4
1.075 0.476 3 -«.5 43.34 22.78 0.91 o-n t 3.059 2.429 48 0 41.94 22.06 1.23 ice 4.13 4.579 24 5.3 41.64 21.65 1.44 benzene 4.84 6.681 •24 13.2 41.10 20.41 2.04 6.86 11.379 24 15.2 40.58 19.64 2.29 7.69 12.953 24 18.2 42.33 20.91 2.77 9.31 15.673 24 18.9 42.06 20.48 2.93 9.84 16.374 '48 20 42.62 20.80 3.17 10.65 17.535 24 21.3 42.55 20.22 3.68 12.37 18.996 24 22.4 42.20 18.98 4.57 15.36 20.316 24 23.5 42.26 17.93 5.68 19.09 21.714ADSORPTION OF DO BALANCE No.3 Deflectionfor dry weight 18.00 mm. me •s. T1 °C 1 Rod mm. Top hook mm. Deflection mm. Agent ;; D O on simple *.P.H û 2 > .2 solid 18.00 0 c Og’ éthc r 4 -25 12.44 21.42 0.2 COL, 4 1.111 0.467 3 -7.5 12.41 21.07 0.52 o-n t. 2.88 2.429 18 0 12.09 20.52 0.75 ice 4.166 4.579 24 5.3 11.96 20.26 0.83 henzene 4.88 6.681 24 13.2 11.15 19.15 1.18 6.556 11.379 24 15.2 10.99 18.86 1.31 7.27 12.953 24 18.2 12.43 20.04 1.57 8.72 15.673 24 18.9 12.45 19.97 1.66 9.22 .16.374 48 20 12.64 19.97 1.85 10.28 17.535 24 21,3 12.41 19.51 2.08 11.55 18.996 24 22.4 12.41 18.98 2.61 14.50 20.316 24 23.5 12.40 18.30 3.28 18.22 21.714
MADE BY WILSON-JONES CO.
