February, 1925
INDUSTRIAL A N D ENGINEERING CHEMISTRY
stirring during the cooling subsequent to boiling. During the time rcquired for the kettle and its contents to cool from, say, 293" C. to 175' C., or even less, the oil is undergoing further change in molecular weight. Owing to this factor, unexpected discrepancies were found in the product on different days, even though the molecular weights were identical in the different batches when the kettle was drawn off the fire. To overcome this difficulty it was found advisable to take samples during the cooling-for example, at. 245" and 220" C., or even 190" C.-and to determine the molecular weight. If the molecular weight a t 245" C. was greater than that of the 245" C. sample of a preceding batch, stirring was discontinued or lessened and further change thus diminished. If, on the other hand, the molecular weight was lower than expected, stirring was made more vigorous; or in case the temperature had dropped as low as 190"C. without a satisfactory molecular weight, the kettle was put back, the fire relighted, and the oil was cooked for a short additional time. The length of time required to get a certain effect, such as a small molecular weight rise of 50 a t 220" C., was determined by experiment for the kettle under consideration and such data used for the short additional heating. The authors have observed that this procedure of putting the kettle back on the fire is not so unusual in well-run cook rooms as might have been expected. The results in the tables in this paper apply, of course, to a particular lot of linseed oil, and cannot be used indiscriminately for all makes of oil. Different shipments of linseed oil will probably give figures considerably different. It is, of
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course, possible to check molecular weights of different shipments against some property such as tensile strength, but no such procedure has been found satisfactory. Therefore, when a new shipment of oil is received it is necessary to boil several batches under careful molecular weight control and to determine afresh the optimum conditions in order to arrive at certain desired results. The molecular weights are large numbers and a small variation in boiling makes a considerable difference in the molecular weight. The variation is therefore magnified and attention directed to it. Continued molecular weight studies on the boiling indicated more strongly than any other criterion had previously done the value of buying and tanking a supply of oil sufficient to last for a considerable period of time and thus escaping annoying or ruinous variations in factory practice due to differences in the oil as received. The method outlined for linseed oil has been followed with China wood oil and enough work done to indicate the use of the method in the boiling of China wood oil for various purposes. The molecular weight increased, for example, from 850 to 987 when the China wood oil was heated for 4 hours at 149" C. The authors are continuing the study of the molecular weight changes during the boiling of China wood oil and are further studying the mechanism of the reactions which occur during the boiling of linseed oil, with a view to fixing the limits of condensation, polymerization, and oxidation, or other phenomena involved.
New Laboratory Apparatus' By Fred A. Wiggers PATHOLOGICAL
LABORATORIES, TOLEDO HOSPITAL, TOLEDO, OHIO
Device for Saving Supernatant Fluids
Distilling Apparatus
N MANY laboratory procedures it is essential to save supernatant fluids. At times this entails the laborious task of pipetting off the fluid by hand. Especially is this true when the volumes are large. There has been no available apparatus in the market for accomplishing this procedure without losing the fluid into the drain pipes. Most of the mechanical decanting has been with the suction pump. With this method it is evident that the supernatant fluids are lost. Q F With the idea of saving much 4 hand pipetting several years ago, t? the writer devised a simple apparatus to collect supernatant fluids. This was accomplished by c o n v e r t i n g a n o r d i n a r y to~~ecf,,,g straight-sided separatory funnel Tube into a receiving funnel. By elaborating this scheme somewhat a funnel was obtained (Figure 1) that seems to meet all requirements. In detail it is a separatory funnel sfoPcock with a closed roof, an inlet pipet Yacuum for the intake of fluids, and a tube leading to the pump. In principle, u,/ef the pump pulls a vacuum in the Figure 1 funnel, and this vacuum, in turn, pulls the fluid into the funnel. The entire operation can be aseptically carried out and the fluid preserved in a sterile condition. The funnel can be used for any class of work.
Every laboratory has had the task of distilling and redistilling alcohol or ether or a mixture of both. Either liquid, especially ether, is volatile and great caution is required in distilling them. I n most laboratories the usual procedure has been to distil them over from a flask resting in a water bath. Such methods are cumbersome and often dangerous. Several years ago the writer had a copper jacket arranged about a Florence flask and placed heated water between the two. This method was not entirely satisfactory where an all-glass still was needed, and so the double-flask still (Figure 2) was planned. This is simply a large flask completely incasing a smaller one, leaving a space for water between the two. In practice, water is allowed to enter through the pipet into the space between the flasks. The water is heated and the temperature regulated by a thermometer thrust into a suitable opening provided for it. Toward the top of the neck of the larger flask is a pet cock with a glass stopper to act as a safety valve for steam. The neck of the inner flask rises above that of the larger one and is provided with an outFigure 2 let tube for the vapor to be passed to the condenser. This outlet tube fits like a ground-glass stopper and the whole apparatus is easily cared for and kept clean.
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Received October 11. 1924.
