.Table IV.
Corrosion Tests at
80” to 90” C.
Inches Penetration per Year X 10-5 Material Tested Teflon-punched cloth Lead 316 stainless steel filter cloth Aloyco 20 disk
Nichrome filter cloth Nickel Monel
52% 1 wk.
PaOs 2 wk.
1 wk.
No change No change 420 75 3680
14% Ptos
28% Pa06 2 wk.
1 wk.
l o change No change 293 50 1970
460 ... 2270
No change
252 ... 1100
362 e . .
1400
Acceptable
174
... 694
Good
Poor Useless Useless
Completely corroded Completely corroded
Coleman, J. H., U. S. Patent 2,384,813 (1945). Zbid., 2,384,814 (1945). Jacob, K. D., “Fertilizer Technology and Resources,” p. 193-4, Academic Press, New York, 1953, Legal, C. C., others, U. S. Patent 2,504,544 (1950). Shoeld, M., Zbid., 2,384,773 (1945).
~~
Phosphoric Acid Impurities (Basis 50% phosphorus pentoxide acid) HnSO4, % 1-5 (laboratory) 6-9 (pilot plant) FezOS, % 0.7-1 AltOa, % 2-2.5 AslOa, p.p.m. 15-45 PbO, p.p.m. Approx. 15 Fluorine, yo 0.10-0.40 Traces of calcium, chromium, vanadium, copper, and organic matter.
The fluorine content is Qonsiderably lower than that of other crude acids. Some samples showed as little as 0.10% fluorine; none contained over 0.4% fluorine. Acid made by other wet processes, if not purified, contains 3 to 6% fluorine. Phosphorus Pentoxide Recovery. In general, phosphorus pentoxide recovery was satisfactory. An over-all yield of 95% phosphorus pentoxide was realized in laboratory work. A minimum yield of 92% and a maximum of %yowere realized in the pilot plant.
70
Calcium Phosphate Analysis, Moisture 18.90 CaO 22.62 Total PZOS 45.00 P ~ Osoluble K in 0.4NRC1 44.70 Free &PO4 2.70 SOa
F Fluorine-phosphorusratio
1.45 0.11 1 to 177
RECEIVED for review September 22, 1956 ACCEPTEDDecember 11, 1956
The ratio of 1 to 177 readily meets the requirement of the Association of American Feed Control Chemists that it must be a t most 1 to 100. Monoammonium phosphate was made by bubbling anhydrous ammonia into the phosphoric acid until a solid product resulted. Monoammonium Phosphate Analysis, Moisture 2.60 Nitrogen 11.00 Total PsO6 54.90 Insol. P ~ O S 0.04 Avail. PzOs 54.86
%
Division of Fertilizer and Soil Chemistry, 120th Meeting, ACS, Atlantic City, N. J., September 1956. .
Corrections
Efficiencies of Mixing Tanks in Smoothing Concentration Fluctuations
0
I n the article on “Efficiencies of Mixing Tanks in Smoothing Concentration 48,1817 Fluctuations” [IND.ENG.CHEM. (1956)] the last part of Equation 6 should read : -2a cos (27rt/X)
Advantages of Process
Product Uses Some work was done on determining the purposes for which the acid could be used. These uses are not new but are well known to the trade. Tests showed that the acid was orthophosphoric acid and could be used for regular purposes. Triple superphosphate of 45.5% available phosphorus pentoxide when adjusted to 5y0 moisture content was made using 72y0 bone phosphate of lime rock. Triple Superphosphate Analysis, Moisture 5.0 Total P103 46.62 Avail.
Rating Excellent Excellent
2 wk.
No change
%
45.50 1.12 5.24
Pi03
Insol. PSOS Free acid ~~
One of the uses for phosphoric acid of low fluorine content is in the manufacture of calcium phosphate for animal food. A product made by reaction of the acid with slaked lime gave the following analysis:
The process has five advantages over other wet processes. 1. Strong (5001, phosphorus pentoxide) phosphoric acid can be produced directly without concentration. Acid of lower strength can also be produced. 2.r The fluorine content of the product is sufficiently low to permit manufacture of animal mineral food supplements directly without a fluorine removal step. 3. The process is versatile, in that phosphoric acid recovery may be effected by the use of either filters or leach tanks. 4. Total process time using the clinker filtration procedure is less than 60 minutes, compared to many hours by other wet processes. 5. Fluorine evolution from the rock is almost 90% complete; this makes possible the recovery of a valuable by product. The clinker process is covered by patent (6)and is available for licensing. literature Cited 1) Chem. Eng. News 34,2452 (1956). 2) Chemical and Rubber Industry Report, U. S. Dept. Commerce, vol. 3, No. 3, p. 7, March 1956.
A pertinent reference not included is: Dankwerts, P. V., Sellers, E. S., Ind. Chemist 27, 395-8 (1951). EDGAR B. GUTOFF
Carboxylic Rubbers from Scrap Vulcanized Rubber
0
In the article on “Carboxylic Rubbers from Scrap Vulcanized Rubber” [Joseph Green and E. F. Sverdrup, IND.ENG. CHEM.48, 2138 (1956)J the formulation a t the top of the third column on page 2143 was incorrectly printed. I t should have appeared as:
L o I
0
I Zn
I
o=c
‘
0-Zn-
I Z=O
I
Zn
I
I
0
OH
I c=o
OH
I c=o
II
I
VOL. 49, NO. 3
1
MARCH 1957
337
