INDUSTRIAL A N D ENGINEERING CHEMISTRY
October 1.5, 1930
419
Improved Vacuum-Tube Falling-Ball Viscometer' Leonard P. Moore and A. C. C u t h b e r t s o n DEPARTMENT OF INDUSTRIAL ASD CELLULOSE CHEMISTRY, MCGILLUSIVERSITY.MOSTREAL, CAXADA
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N AY attempt to correlate the extent of the degradation of cellulose, by the action of sulfurous acid and bisulfites, with the change in viscosity of a solution of the cellulose in cuprammonium hydroxide, a falling-ball viscometer was required similar to the one described by Symmes and Lantz ( 1 ) . After experimenting for some time with the circuit as described by them, it was found to be unstable and not sufficiently sensitive to permit measurements to be carried out with steel balls as small as inch (3.2 mm.) in diameter. By two simple additions the usefulness of the apparatus has been somewhat extended. Apparatus
The circuit, as shown in the figure, is essentially the same Two variable air condensers, of the capacities indicated in the diagram, have been added, one shunted across the phones and the other across the plate coil. as that described by Syrnrnes and Lantz ( 2 ) .
VISCOMCTCR
T U B E A N 3 OSCILLATOR
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plate coil. If this oscillation were properly adjusted, the effect of the passage of a ball through the coil was sufficient to stop the oscillation momentarily, thereby permitting accurate timing of the fall of the ball between the two coils. I n the case of very viscous solutions the ball stops the oscillation for a perceptible length of time. The rate of fall can be quite accurately determined, however, by taking the time between the points where the oscillation initially stops. A condition of null oscillation is preferable to a gradual change in note. The ratio of the inductances of the plate to the grid was not found to be critical and the dimensions given by Symmes and Lantz were very satisfactory. The viscometer tube used in conjunction with the vacuumtube circuit was made of Pyrex and of the dimensions shown in the figure. On the outer side of the two coils hard-rubber disks were fixed to the tube. They served two purposesthe prevention of corrosion of the coils when filling the tube or when cleaning it; and, of more importance, easy replacement of the tube in a vertical position in a thermostat. The second purpose was accomplished by making the disks of such a size that they would just slide into a long glass cylinder which, in turn, was closed at the bottom and was fixed rigidly, a t all times, in a vertical position in a water thermostat. It has been found possible to use both steel and aluminum balls, the latter, however, in the l/rinch (3.2-mm.) size did not give consistent results. The results for the time of fall through a Bureau of Standards oil (viscosity, 9.60 poises a t 20' C.) will illustrate the accuracy of the method.
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STEEL BALLS '/4-in. (6.4-mm.) Sec. 7.0 7.0 7.0
7.0 7.0
3;10-1n. (4.8-mm.)
'/*-in. (3.2-mm.)
ALUMINUMBALLS 1 /h-in. 3i16-in. (6.4-mm.) (4.8-mm.)
Sec.
Ses.
Sec.
Sec.
5.5
12.4 12.4 13.4 12.4 12.4
18.5 18.5 18.5 18.5 18.5
27.0 27.0 27.0 27.0 27.0
i;; ;.
a.0
I n the work for which the viscometer was required, it was used over a relative viscosity range between 5 and 200 poises. L i t e r a t u r e Cited (1) Symmes and Lantz, IND.ESG. CHEM., Anal. Ed., 1, 35 (1929).
Flax as Paper-Making Material The phone condenser, together with the grid leak, permits a steady note to be produced at a frequency best suited to the individual ear taking the reading. Without this condenser the frequency of the note varied during a measurement, so that it was difficult to differentiate between it and the effect of the ball passing through a coil. The highest sensitivity of the apparatus appeared t o occur when the vacuum tube was ''just" oscillating. This condition was attained by first obtaining the desired note, as suggested above, and then adjusting the tube oscillation by means of a vernier attached to the variable condenser shunted across the 1 Received June 9, 1930. From a thesis presented by Leonard P. Moore to the Faculty of Graduate Studies and Research of hlcGill University in May, 1930, in partial fulfilment of the requirements for the hl. Sc. degree.
The Bureau of Standards has been making an investigation t o determine the paper-making value of New Zealand flax. Samples of the flax-unscutched, scutched, and tow-which a t present is used commercially only for cordage, were submitted to the bureau with request for information relative t o the suitability of the material for the production of paper. Paper-making tests have been made on both laboratory and semi-commercial scales. The test procedure followed was essentially the same as that generally observed in the production of paper. Cooks were made using caustic soda, caustic soda and sodium sulfide combined, and sodium sulfite and caustic soda separately, as the reducing agents. The results of the tests thus far seem to indicate that, if the flax can be properly cleaned, freed from dead fibrous materials, and the woody sections eliminated from the scutched material, a fair grade of pulp suitable for use with other pulps in making a fine paper can be obtained. As soon as the investigation is completed, a report of the work will be prepared for publication.
