2 98
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 17, No. 3
Comparison of Various Glues
A
Hide and fleshings
236
191
AEx
17.5
38.5
739to800
10,50Oto11,350
217
3085
5.8
83.0
B
Bonecalf
170
130
1 Ex
16.5
36.3
817 to894
11,600 to 12,700
...
...
4.7
67.8
C D
Hide
176
146
1 Ex
13.5
29.7
711 to810
10,100to 11,500
258
3665
5.4
78.0
First-run hide 160
138
li/r
13.0
28.6
697 to746
9900to 10,600
261
3700
5.3
75.3
140 118
118 116
11/2 11/4to IT/:
11.5 9.0
25.3 19.8
711to725 317to460
10,10Oto10,300 4500to 6540
277 185
3840 2635
4.0 3.3
57.0 47.1
E F
Bone Junkbone
heating gradually in thezviscometer cup and stirring until 60” C. (140’ F.) is reached, when the viscosity is read using the MacMichael instrument. This was done by different observers two years apart, which accounts for the difference in the results. Results In the accompanying table the first four columns of figures are those of the manufacturer. They are his arbitrary ratings and valuable only for comparison with each other. The jelly test and viscosity (done with a glass pipet) agree remarkably well, being, as Bogue says, “parallel functions.” T h e addition of hide stock to bone glue seems to increase both jelly test and viscosity, and fleshings seem to raise them still further. Whether this is generally true remains to be seen. I n the last nine columns it is to be noticed that the actual tensile strengths of all the glues except junk bone are approximately the same. The diminution in strength is probably due to the hydrolysis of the gelatin of the glue while being made. This uniformity of strength excludes this test as a means of discrimination.
24.0 25.2 13.5 13.1 14.0 15.3 26.0 21.0
Where actual strength is of importance, there is little advantage in using a high-grade glue. This is also true in the sand-paper industry, where a medium quality of glue is employed. Since the tensile strength of glue is about 704 to 845 kg. per sq. cm. (10,000 to 12,000 pounds per square inch) and wood 1408 to 2112 kg. per sq. cm. (20,000 to 30,000 pounds per square inch) and that of a glued joint about 352 kg. per sq. cm. (5000 pounds per square inch), the care taken in making this joint-the perfection of the union of glue and woodis the important factor. The strength determined by the bibulous paper test is in accord with the jelly and viscosity tests. It is to be noticed that the absolute viscosity does not agree with the pipet viscosity in the case of Sample D, first-run hide. Acknowledgment Acknowledgments are due Messrs. Codwise, Hale, Davis, Hanson, and Chirgwin, by whom the experimental work has been performed.
A Laboratory Circulating Pump for Corrosive Vapors’ By H. C. Kremers UNIVERSITY OF ILLINOIS, URBANA, ILL.
I
N ONE phase of researches on the rare earths in this
laboratory, large quantities of anhydrous chlorides of the rare earths are continually being prepared. It has been found by most workers that these chlorides are best and most conveniently dehydrated in a stream of dry hydrogen chloride gas. Since the rate of dehydration is then a function of the rate of flow of hydrogen chloride vapor, it is quite evident that large quantities of this gas must be generated in order to dehydrate any quantities of material. Quantities as large as several kilograms of rare earth anhydrous chlorides thus require many days in preparation, not to mention the inconvenience of generating large volumes of hydrogen chloride. As a result of these conditions and in attempting to speed up this operation by greatly increasing the flow of hydrogen chloride vapor, the circulating pump shown in the accompanying diagram was designed. Hydrogen chloride is generated by the action of concentrated sulfuric acid on sodium chloride. The latter is first well soaked with concentrated hydrochloric acid solution. The gas is dried in the usual manner by passing through the tower, 2. This tower is, of course, filled with glass beads and kept well moistened with concentrated sulfuric acid. The furnace, 9, of the ordinary chromel-wound type, contains a glazed porcelain core 75 mm. x 450 mm. with 1 Received
January 1, 1925.
a flange a t 8. This flange and the cap to fit have been made into an ordinary flat-ground joint similar to a desiccator and cover. By making a gasket of asbestos paper moistened with dilute water glass, and clamping on the cap, a joint perfectly tight to hydrogen chloride is made, which is capable of withstanding considerable heat. The incoming hydrogen chloride is preheated by the coil 7. The most satisfactory cement for attaching the preheater tube 7 to cap 8 is composed of very fine alundum cement moistened with dilute water glass. Upon drying and a t a few hundred degrees heat i t forms a hard semivitrified mass. The action of the circulating pump is clear from the diagram. The outer jackets, 5, are made of 50-mm. glass tubing and are about 700 mm. long. The inner plungers are, of course, sufficiently smaller in diameter to allow free action. Connecting rods are attached to the plungers by means of short pieces of brass tubing set over the projections on the plungers and then filled in with sealing wax. The remaining driving mechanism is self-explanatory and can be constructed to suit individual tastes and conditions. The liquid seal used in the jackets, 5, is a saturated paraffin oil, although concentrated sulfuric acid, or even mercury, might be used to advantage, depending upon conditions or gas used. The intake, 3, and outlet, 4, valves are made of glass and the valve seating is flat enough to prevent sticking of the valve during operation.
March, 1925
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
Under normal operation this pump will circulate 10 liters of gas per minute. The condenser, 10, will condense the excess moisture coming from the material in the furnace, 9, and is trapped out in bottle 11. The still moist gas is then forced through tower 2, dried, and again circulated through the pump and furnace. The trap 12 acts as an excess pressure outlet, and by continually generating a small flow of fresh hydrogen chloride from 1, the gas in the entire apparatus is under a slight pressure and leakage of “air in” is entirely eliminated. In the former type of dehydrating furnace in use in this
research, holding about 150 grams of rare earth chloride a t one charge, without the use of the circulating pump described above and with only the hydrogen chloride generator, 1, in use to supply the flow of gas through the furnace, the time for dehydration was about 24 hours. In the apparatus as described herein, with the larger furiiace holding a 400-gram charge and with the use of the circulating system, the time of dehydration is cut down to 6 hours. This equipment has been in operation part time for 18 months. About 25 kg. of material have been dehydrated with entire satisfaction.
1
HCI
2
!%SO+ DTyiiIg ToweT
Generato1
3
Intake Valves of Pump
4
O u t l e t Valves of P u m p
5
O u t e r JacheT of P u m p
6
flovable 88115
7
PTe healeT
a
Asbestos-WateT qlass Gasket
9
DehydTatlnq Furnace
10 11 12
29g
or
Plungers
Con dens eT Wa‘lCT TTa p Excess P T e s s u r e O u t l e t
Weatherproofing of Gypsum Block Gypsum, though satisfactory as a plaster and tile for interior work, has not proved satisfactory for exterior construction, because of its slight solubility in water. If this material could be so improved as to be more resistant to the weather, there would immediately be opened a new market for gypsum block. It is probable that if a method is found whereby gypsum block can be weatherproofed, the procedure may easily be modified so as to include such other products of gypsum as stucco, mortar, etc. With this in mind an investigation of methods of weatherproofing gypsum has been undertaken by t h e Bureau of Standards. In attacking this problem three general methods presented themselves: first, covering the set material with some waterproof coating to keep the moisture from the gypsum; second, precipitating on the surface a n insoluble compound formed by a reaction of some material with the gypsum; and third, adding an integral waterproofing compound to the gypsum, which when the gypsum has sat acts as a water repellent. In the beginning of the investigation many small cylindrical specimens of gypsum were made and treated in one of the ways described above, and then exposed t o the weather. At definite intervals these were dried, weighed, and tested for absorption. At the end of one year’s exposure, panels were made of the same composition as the small cylinders, which upon examination gave promise of satisfactorily withstanding the weather. These panels were exposed to the weather, and are now examined from time to time. The first method has so far given very promising results. Waterproof paints, varnishes, shellacs, whitewashes, paraffins,
waxes, stearic acid, etc., have been used The paints, varnishes, shellacs, and whitewashes were not satisfactory, but with paraffin, waxes, and stearic acid very good results were obtained. However, the second method has so far proved the most successful. Cylinders of neat gypsum and 1: 1 sanded gypsum were made, and when approximately dry were immersed in solutions of barium chloride, sodium carbonate, ammonium phosphate, ammonium oxalate, lead acetate, and barium hydroxide. The results obtained with all the salt solutions did not warrant the recommendation of any of them as weatherproofing materials. I n the case of hot barium hydroxide, however, the results were very promising. The success of this material as a means for weatherproofing gypsum is explained by assuming that the barium hydroxide, which penetrates the pores of the gypsum, reacts with the calcium sulfate to form the more or less insoluble compound, barium sulfate. This very slightly soluble barium sulfate coating on the surface of the gypsum cylinder makes it very resistant to the weather. This protection is only temporary, however, for after a period of approximately two years’ exposure the cylinders begin to weather away about as fast as do the cylinders of untreated neat gypsum. After this period it is probable that another application of the barium hydroxide solution would protect the gypsum for a similar length of time. This is being investigated. The third method has not given promise of good results. Among the integral waterproofing compounds used have been zinc stearate, glue, gum tragacanth, gum arabic, glycerol, dextrin, and water glass. None of them seems to waterproof the gypsum for any length of time.
