Electron Diffraction Camera
A
N ELECTRONIC vacuum camera that photographs the crystalline structure of substances millionths of an inch thick has been built by Dr. Ralph P. Johnson of the General Electric Research Laboratory. The camera is being used to study deposits on the surfaces of nktals, e. g., tarnish, polish. lubricants such as grease and oil, and the first stages of corrosion. It supplements X-ray apparatus that permits study of the interior of substances of greater thicknesses. The camera proper consists of a brass tube about three and one-half feet long and a focusing magnet. A 40,000-volt electronic beam enters one end of the tube, is focused by means of the magnet upon the material suspended in the middle of the tube, di&acts, and produces a picture upon a lantern slide at the other end of the tube. The tube is evacuated to permit free gassage of the electronic beam without colksion with gas molecules. The material to he photographed is suspended in such a way that it can be raised or lowered or tilted at any angle to the beam.
material and a diffraction pattern is produced upon the lantern slide. The spacing and intensity of the circles or spots of the pattern enable the physicist to determine thecrystallinestructure.
(a)
(bl
ELECrRoNIC DIPPRACTION PATTERN OI. (a) SODIUM CHL.oRIDI3 n m (b) GOLD
I
T IS reported in the Industrial Bullelin of A. D. Little. Inc., that the Bessemer steel process is taking a new lease on life. Its one main advantage has always been its rapidityahout 18 minutes to "blow" 25 tons of steel. as compared with 10 t o 11 hours for the treatment of 150 tons in an open-hearth furnace. But the speed has prevented accurate control and uniformity of product. The end of the blow must be determined with great accuracy to insure success, and this is now being accomplished by means of photoelectric cells. Another drawback of the Bessemer process has been the impassibility of removing sulfur and phosphorus. Recent improvements have removed this disadvantage. Pretreatment in a ladle with soda ash takes care of mast of the sulfur. Phosphorus is removed in a slag, formed by the addition of lime, iron oxide, and fluorsparto the blown metal after pouring. In 1939 about 3.5 million tons of Bessemer steel were made out of a total of about Fh? million tons. This vear 15 million out of a
Similar cameras have been built by the Bell Telephone Laboratories and others. The electronic beam is reflected by or transmitted through the
ber of new products from the Searles Lake brines. These materials, which represent 40 per cent of the company's tonnage, include soda ash, salt cake, burkeite, bromine and bromides, potassium sulfate, and lithium phosphate. All these except the last are commonly manufactured products, but it is very uncommon to find them as by-products of natural occurrence, as they are in these brines.
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