A STUDY OF THE SHRINKAGE OF DIASPOR CLAYS.—PART I1

Diaspor refractories often possess the undesirable characteristic of continual shrinkage in service, and since it is not practical to alter such properties in the present manufacturing processes, the object of this study was to devise, if possible, a manufacturing process to overcome this shortcoming. This part of the paper reveals the mechanism of the firing shrinkage and describes the effect of particle size, time and temperature upon the shrinkage of diaspor clays of various compositions. The properties of the two major constituents of a typical sample are given, as well as photomicrographs of interesting samples. Part II will describe experimental work conducted to devise shrinkage processes and the properties of products so made.     

A STUDY OF MULLITE REFRACTORIES FORMED BY CALCINING CYANITE,THEIR INDUSTRIAL APPLICATION1

This paper is a progress report of an investigation dealing with refractory bodies made of cyanite, either raw or calcined, and which was taken from a recently discovered deposit in India. The bodies were subjected to standard and modified laboratory tests for high grade refractories. Petrographic analyses indicated complete conversion to mullite in the test specimens and the results of the laboratory test indicate the bodies to be equal in quality to many so-called “super-refractories” now on the market.     

E-90-P COMPARATIVE TEST OF HAMMER MILL PULVERIZER AND DRY PAN FOR CRUSHING STREATOR SHALE1

In the machines as described below the following points are discussed: (1) the grinding action, (2) energy consumption per ton ground, (3) capacity to produce fines six-mesh and under, (4) to determine the operating characteristics of the hammer mill. The conclusions given are: (1) The dry pan will not grind shale chunks larger than 15 inches maximum diameter, nor chert nodules of any size. The hammer mill grinds easily in one operation all chunks small enough to go through the 20 × 42-inch hopper opening and all chert nodules. (2) The energy consumption of the dry pan as compared to the hammer mill in kw. hrs. per ton of fines through six-mesh is approximately as 1.40 to 1.25. (3) The maximum capacity of the Frost %foot dry pan with 1/4-inch screen plate openings was known to be approximately 25 tons through six-mesh per hour. The maximum capacity of the 30 × 42-inch Williams hammer mill as reached in these tests with hand feeding was found to be 56 tons total feed and 42 tons through six-mesh per hour. This figure could have been greatly exceeded if the material could have been fed more rapidly. The dry pan tailings coarser than six-mesh compared to the hammer mill tailings of the same coarseness are as 40 to 25%. (4) The hammer mill is more efficient than the dry pan in practically all respects if properly set up and operated, but it is easily possible to secure less efficient results from the hammer mill, particularly if the feeding is not properly regulated.     

Digestibility of fats taken from the animal body

Summary The digestion experiments reported above were all conducted under like experimental conditions, thereby making possible a close comparison of the results obtained for the individual fats studied. The fats under consideration were obtained from different parts of the body of cattle but due to the amount of fat required for even three or four digestion experiments it was impossible to use fats from only one animal. In comparing the digestibility of fats from the different parts of the body it is interesting to note that brisket fat, butter, cream, and oxtail fat were equally well absorbed, being 97% digested and hard-palate fat, kidney fat and ox-marrow fat were 94% digested. While the difference in digestibility, 97% to 94%, is not large, one can hardly avoid speculating as to why the animal body should produce fats as far as digestibility is concerned fall into two distinct groups. None of the fats studied produced other than normal physiological reactions, except ox-marrow fat, but with this fat each of the four subjects experienced digestive disturbances as the result of the ingestion of 59 grams of ox-marrow fat daily, which would indicate that the limit of tolerance for this fat was much lower than for other beef fats. With the possible exception of ox-marrow fat, all the beef fats are very completely digested and are well tolerated by the human body. Note: Since fats from cattle are included in nearly all diets, the following resume of digestion experiments, conducted by the author while employed as physiological chemist at the U. S. Dept. of Agriculture, is given to supply information concerning the digestibility of such fats when included in a simple mixed diet.