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INDUSTRIAL A N D ENGINEERI,%-G CHE;MISTRY
those of the silicates with the same solutions. The products of the aluminate with sulfates depend on the concentration of the sulfate, whereas with the silicates the products are the Same regardless of the sulfate concentration. The extreme fineness of the sulfoaluminate crystals formed with concentrated sulfate solutions and tricalcium aluminate indicates that these crystals were formed very rapidly. The crystalline aluminate grains last longer in the more concentrated sulfate solutions, a layer of clear gel surrounding them. In the 2 per cent sulfate solution the sulfoaluminate crystals grew to the largest size, forming in the case of the hydrated aluminate extremely long needles, the felting of which caused the suspension to become semisolid in 20 days. Further experimental work is being done on mixtures of crystalline tricalcium aluminate and very dilute solutions of sodium sulfate. In these mixtures sulfoaluminate crystals are first formed, then disappear and crystals of hydrated tricalcium aluminate grow to a large size. Both gypsum and sulfoaluminate crystals were formed in mixtures of magnesium sulfate with crystalline and also with hydrated tricalcium aluminate. Sulfoaluminate appeared in the dilute (0.5,2 and 0.5, 1, 2 per cent) and gypsum in the other solutions. Sulfate solutions act on crystalline tricalcium silicate in somewhat the same manner as water alone, since a gelatinous coating is formed on the grains, the centers of which gradually grow smaller and finally disappear. However, this change proceeds a t a more rapid rate with sulfate solutions and goes to completion in a short time, no crystalline particles being left. An important difference in the two reactions is the formation of gypsum crystals in the sulfate solutions, thus removing the free calcium hydroxide that is formed during hydration of the silicate in water alone. No explanation can be given for the breaking up of the amorphous silicate grains into very small particles in the saturated solution. It may have been due to the formation of minute gypsum crystals in the gel, but such crystals were noted in only one case. On the whole, solutions of magnesium sulfate had a more destructive effect on the constituents, especially in the hydrated forms, than those of sodium sulfate. Two exceptions were very pronounced. I n one case, grains of crystalline tricalcium aluminate in magnesium sulfate solutions were covered with a gelatinous layer, which protected the centers from further action of the solution. The largest centers were in the 8 per cent and saturated solutions. In the other case, in the hydrated tricalcium silicate mixture with magnesium sulfate, crystals of lime were covered with a layer of amorphous magnesium hydroxide, which caused these lime crystals to persist for a much longer time than they did in the solutions of sodium sulfate. The reactipns with dicalcium silicate are characterized by the slowness with which they proceed. In an attempt to hydrate the dicalcium silicate completely, a sample was ground very fine, shaken with water, and the coarser grains were allowed to settle. The suspension of fine grains was poured off and shaken for about 3 weeks, with the result that all the solid adhered to the walls of the flask and the liquid was clear. Some of the solid was scraped off and on examination showed clear grains of gel with no crystalline centers.
Vol. 17, No. 6
Automatic Buret and Flask for Standard Alkali Solutions' By H. R. McMillin h.ISAT I N S P S C T I O N LABORATORY,
BUREAU OF ANIMAL INDUSTRY, c.
~ r A S H I N O T O N ,D.
The Pyrex glass flask is far superior to a flask with a coating of ceresin
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to a collar made of wire placed somewhat below the neck of the flask. The Peligot tube contains a solution of potassium h y d r o x i d e , c which, in connection the chlo- '1-3-liter flat-bottom Pyrex glass 6ask ride tube, which con- B-Subedte ring, 17 cm. outside diameter C-Peligot tube 13 cm. tains soda lime, D-Calcium chlbride tube, 13 cm. to keep out carbon E-3-way glass stopcock, 50 cc. buret F-Spiral wire springs (two not shown) to dioxide and to remove hold suberite ring to flask this gas from the in- &Lead disk weighing abo3t 1000 grams that fits inside the suberite ring to prevent flask from tipping when only a small coming air when the amount of solution is in the 6ask alkali is drawn into the buret. The potassium hydroxide solution in the Peligot tube prevents evaporation of the standard alkali. As the apparatus is free from attachment to the wall or any fixture, it can be shaken and the condensation which Acknowledgment collects on the inside walls of the flask can be mixed with the standard solution, thereby preventing alteration in its strength. The author acknowledges his indebtedness to T. Thor- The three-way buret allows any solution not used to be revaldion for the suggestion of the problem and for helpful dis- turned to the flask and saved. The buret may then be cussions as the work progressed. He also expresses thanks washed with distilled water and damage, due to alkali left in to W. G. Worcester for the use of equipment and materials it, prevented. in the Department of Ceramic Engineering, and to S. Baster1 Received April 10, 1925 field for criticism of the paper.
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