October, 1927
INDUSTRIAL A N D EiVGlNEERING CHEMISTRY
Analytical chemistry and scientific methods of control are, of course: extremely important in enabling the manufacturers of grinding wheels to secure uniform products. The raw materials for abrasive manufacture are analyzed; chemical, as well as electrical, control is exercised over the operation of the electric furnaces; bonds are mixed according to the analyses of their ingredients; and pyrometers and ceramic cones control the temperatures in ovens and kilns. Kew materials are continually being developed and tried for abrasives and bonds. Old materials are being studied and modified to meet demands for different grinding action. hlethods of manufacture are being bettered in order to produce more uniform products. Mechanical designs of wheels and machines are being improved. Abrasives are being introduced into new fields. The future of grinding is bright, and science points the way toward new achievements.
tained by impregnating the grinding wheel itself with materials that soften a t the surface of the wheel under the heat of grinding. Wheels used for dry-snagging of aluminum often cut faster and wear less when impregnated with a proper mixture of fats and waxes. Rosin is sometimes used as a filling treatment for steel-snagging wheels, but its use has largely been developed empirically. A thorough scientific investigation of the general subject of filling treatments and lubrication as applied to grinding should yield valuable results. Achievements through Scientific Methods The petrographic microscope and microscopic methods in general have proved invaluable tools for the study of abrasives and grinding wheels. Examples have already been given of photomicrographs showing a few of their many applications. [ENDOF
1131
SYMPOSIUM]
Colorimeter for Precise Matching of Solutions in Nessler Tubes’ By John H. Yoe UNIVERSITY OF VIRGINIA,
I
S DEVELOPIXG a quantitative colorimetric method
for determining small quantities of aluminum in salts, water analysis, etc., by means of the dye aurin tricarboxylic acid (Aluminon),* recently described by Hammett and Sottery3 as a new qualitative reagent for aluminum, a simple colorimeter was devised to assist in securing a precise matching of colors in Nessler tubes. This colorimeter (Figure 1) is similar to the well-known Kennicott-Campbell-Hurley ~olorimeter,~ a series of Nessler tubes and a rack replacing the stand carrying the two comparison cylinders and reservoir tube. The light (north sky) is reflected by a small mirror placed on the rack at a n angle (not shown), just below the “unknown” and comparison tubes. The light passes upward through the two Kessler tubes, impinges on the two mirrors, A and B, 32 by 19 111111. and 32 by 35 mm., respectively, which are fastened to the wooden box a t an angle of 45 degrees, and is reflected horizontally through the metal observation tube. Half of the circular field of light from the right-hand tube is cut off by mirror A, the vertical edge of which serves as a dividing line between the two halves of the circular field. The image of half of the right-hand tube is then observed in juxtaposition to the opposite half of the image of the lefthand tube. The juxtaposed images are observed through a thin metal tube, 170 mm. long and 25 mm. in diameter, painted dull black inside and out and provided with an eyepiece having a hole 1.5 mm. in diameter. At the other end of the tube is a diaphragm having an aperture 8 mm. in diameter. By having the apertures in the eyepiece and diaphragm properly proportioned only the image of the bottoms of the Nessler tubes can be seen, thus preventing interference of light reflected from the vertical sides of the tubes. Upon looking through the eyepiece the observer sees a single circular field divided by an almost imperceptible line when the two solutions have the same intensity. The colorimeter is athched to the Nessler rack by means of a metal tube support which slides snugly down over a 1 Received May 14, 1927. Contribution No. 40.
CHARLOTTESVILLB, VA.
vertical rod securely fastened to the rack. It can thus be quickly and easily raised and turned on its horizontal axis, permitting interchange of the Nessler tubes in the series of standard solutions until a match with the “unknown” is obtained. I n practice, the approximate match is first obtained in the usual way by looking down vertically through the tubes in the rack and then the final match made by swinging the colorimeter into place. The colorimeter box is painted dull black inside and out. It is fitted with a removable cover, which permits easy access to the mirrors for the purpose of adjusting and cleaning. .Nibor A or B
Figure 1-Colorimeter
for Nessler Tubes, Vertical Cross Section
A screen made of a piece of s t 8 cardboard and painted dull black may be interposed between the Nessler tubes and the source of light. A colorheter lamp is recommended if the highest precision of matching is required. In such a case a white glass plate makes a better reflector than a mirror.
New Argentine Chemical and Metallurgical DevelopmentA company, capitalized at 5,000,000 paper pesos, has been organized in the Province of Mendoza to develop Argentine copper mines by the iodide process, by which the company ex* TBe finally adopted method and the results of an extensive study of pects t o produce hydriodic acid, sulfuric acid, copper sulfate, and it will be published later by J. H. Yoe and W. L. Hill ( J . Am. Chem. Soc., chemically pure metallic copper. Apparently, the promoters of in press). the project have based their calculations on the results obtained a J . Am. Chem. Soc., 47, 142 (192.3. a t the iodide plant in Santiago, Chile, which was inaugurated on 4 Kennicott and Sargent, Chem. Eng., I , 213 (1906-7); Campbell and February 26, 1926. Further details are available in the Chemical Hurley, I A m . Chem. .Soc.. 33, 1111’ (19111: Smeaton, Ibid., ‘28, 1433 (19061. Division, Department of Commerce.
