I N D UXTRIAL A N D ENGINEERING CHEMISTRY
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repairs except occasional painting, and it seems to be in as good condition to-day as the day it was installed. There is no reason why it should not continue its satisfactory service for a long time. Fig. 1 shows a cross section of the tank, which has an overall length of 8 ft. 7 in. and a diameter of 5 ft. 0 in. The
FIG. 2
heads are bumped outward, and the capacity of the tank is about 15,000Ibs. of 20' BB. hydrochloric acid. It is mounted transversely on a flat car, as may be seen from Fig. 2. Fig. 3 is a close-up of the openings in the tank. The joint between the head and the body is made tight with a soft-rubber gasket, which has given no sign of leaking. I n the case of a larger tank, entrance to which could be gained through a manhole, this gasket would be unnecessary, the lining of the whole tank being continuous. However, during the process of lining one end has to be removed, but after being replaced the joint between it and the tank could be vulcanized, thus eliminating one possible source of leakage. Since the method of making the lining adhere and of taking care of the differences in the coefficients of expansion of the hard rubber and the steel is of interest, these points will be briefly discussed. A laminated lining, consisting of a layer
FIG. 3
of soft and a layer of hard rubber, is cemented to all interior surfaces, and is then vulcani~edin position, under considerable pressure. The outer layer of hard rubber then comes in contact with the liquid to be handled, while the under layer of live, soft rubber, so firmly bonded to it and to the tank that
Vol. 15, No. 2
it is practically impossible to pull it off, exerts a cushioning effect between the two harder layers. This cushion not only allows for differences in the rate of expansion of the two hard layers, but protects the inner lining in case the outer one is subjected to a blow. I n the extreme event of the inner lining being broken as the result of an extraordinary shock, such as might be experienced in a train wreck, the soft-rubber backing will still hold, even if the tank is dented, allowing the acid to be drawn off at leisure without damage to the steel of the tank or car. This experimental tank was built as simply as possible and is emptied with a soft-rubber siphon. There would be no difficulty in providing a tank with a permanent hard-rubber standpipe, for emptying with compressed air, provided the steel tank was designed to stand the necessary pressure. This tank also, while designed primarily for hydrochloric acid, can be used with any other liquid which does not attack hard rubber, such as acetic acid, citric acid solution, caustics, etc. Moreover, because of the nonabsorptive properties of the lining, a single tank can be used for a number of different materials, as it is very easily cleaned by simply flushing out with water. At present it is impossible to give even approximate cost figures, though if such a tank is adopted as the standard shipping container for hydrochloric acid, and specifications are drawn up for it, it should not be difficult to arrive a t a cost figure shortly. Our present feeling is that, if continued service with this tank proves as satisfactory as our experience to date, there is little doubt but that the du Pont Company will ultimately go to this type of construction entirely.
The Detection of Salt in Stock Feeds' By H. E. Gender BUREAU
OB
CHEMISTRY, PENNSYLVANIA DEPARTMENT OB AGRICULTURE, HARRISBURG, PA.
In the microscopical examination of stock feeds difficulty is often experienced in finding or identifying actual crystals of salt when salt is claimed to be one of the ingredients. Various modifications of the silver nitrate test may be applied, but, except under certain conditions, such tests will only indicate the general presence of chlorides usually present in most feeds, but will not conclusively show the presence of common salt itself. For example, a molasses feed will give a free test for chlorides, although salt as such may not be present. After studying the problem, a simple and accurate procedure was devised which required less than a minute to perform: Transfer 2 cc. of a 5 per cent solution of silver nitrate to a small test tube of 1-cm. internal diameter. Carefully add to this liquid an equal volume of the feed, which has previously been ground to pass a millimeter sieve, so that most of the sample floats or remains above the liquid. Upon gradually inclining the tube, the liquid is absorbed and white patches of silver chloride appear wherever the minutest crystal of salt may lie or be in contact with the side of the test tube. These patches may easily be observed with a lens or even with the naked eye. 1
Received January 11, 1923.
A deposit of diatomaceous earth in Calvert County, Maryland, has been' opened and the product is being refined by the Dashiell Mining & Refining Company. It is stated that the deposit is pure white and free from foreign matter, and that tests have been made which indicate that brick made from this earth possess high insulating qualities.
