Jan., 1918
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
5 0 cc. are titrated with
0.1 N
acid, using methyl orange. The filtrate is then diluted t o t h e desired concentration, which can be done with sufficient accuracy b y measuring the filtrate and the diluting water into a 4-liter bottle with a 500-cc. graduated cylinder. The accuracy of the dilution is confirmed b y titrating I O O cc. of t h e diluted solution. A 0.01 N solution is used as this concentration is fairly stable provided the containing bottles are kept stoppered. It was not found necessary t o displace t h e air in t h e flasks with carbon dioxide during determinations when this concentration was used. The calcium carbonate which settled when t h e liquid was decanted is returned t o the syphon which is rechai-ged and set aside until a fresh solution of bicarbonate is required. While the 0.01 N solution is fairly stable and may be kept under pressure, it is better, however, t o prepare t h e bicarbonate solution fresh each day. Any solution remaining unused from the previous day may be added to the fresh solution before filtration. HAWAIIAGRICULTURAL EXPERIMENT STATION HONOLULU, T. H.
REVERTED PHOSPHATE B y CARLTONC. JAMES
TABLEI-PER
CENT WATER-SOLUBLE
PHOSPHORIC
ALLOWEDTO
B-LIME
3 I
8
11 14 16 20 24 29 35 48
;:is .... ....
6.08 5.37
....
8.6
.... .... 5.67 ....
6.72
4.6
.... 5.08 .... 4.47 ....
7.5 6.63
....
5.39
....
4.72
....
....
3.98
3.82
....
2.44
.... ....
2.23
4.8 4.59 4.47
4.3 3.8 3.54
3.55
2.97
....
7.6 7.0
ACID
IN
MIXTURES
STAND
A-ACID PHOSPHATE & GUANO Period of --MIXTURE-Standing No. 1 No. 2 No. 3 No. 4 On mixing 9 . 1 2 days
33
....
....
SUPERPHOSPHATI3 & L I M E
MIXTURE CONTAINING Period of 15% 30% Standing Lime Lime On mixing 1 5 . 8 1 13.02 6.93 2days 10.17 6.23 6 9.05 8.34 5.52 l14 o 7.87 5.05 4.70 18 7.23 21 7,23 3.82 25 6.99 3.98 4.58 28 6.76 35 6.64 4.19 4.11 40 6.46 5.67 54 6.51 5.62 68 6.46 45 8 0.93 4.60 2.90 1580 0.48
were prepared, t h e constants of which were acid phosphate and brown guano, the name given t o a low-grade Laysan Island phosphate containing coral sand. The variable was lime, CaO. Each sample contained 2 0 0 g. acid phosphate and 2 0 0 g. brown guano: in addition, No. I contained 7.4 g. of lime, the theoretical amount t o revert all water-soluble lime phosphate, disregarding whatever effect t h e calcium carbonate in t h e brown guano might have. No. 2 containqd twice as much lime, 14.8 g. To Nos. 3 and 4 were added 2 g. and 4 g. of lime, respectively. The samples
Received August 28, 1917
As there has been so much published recently concerning t h e reversion of acid phosphate, its value after reversion, and its effect upon plant growth, i t seems advisable t o set forth some of t h e work done b y t h e writer along these lines during t h e last eight years. This work was inaugurated and continued in order t o control better t h e complete fertilizer mixtures, a n d to provide a more effective phosphate for soil conditions in Hawaii. Moreover, t h e contradictory results and opinions of investigators and control chemists elsewhere has made i t necessary t o verify or disprove them when applied t o conditions in Hawaii. It has been generally held t h a t iron and aluminum phosphates are of little value as a source of phosphorus. Now comes a recent publication b y McGeorgel showing t h a t in sand cultures with millet, ferric and aluminum phosphate produced more vigorous plants t h a n acid phosphate, sodium phosphate, phosphate rock or Thomas slag. Similarly, it has been held t h a t reverted phosphate is of less value t h a n acid phosphate. Considering t h e results obtained here b y a n acid phosphate which has been reverted, we are inclined t o believe t h a t under certain conditions prevailing in Hawaii, reverted phosphate gives t h e better results. E XP E R I Y E N T A L
I n a previous article2 the writer showed t h a t some reversion may be expected from the action of lime, carbonate of lime, and a mixture of carbonate and phosphate of lime in mixed fertilizers. I n this article methods, means and materials used t o revert t h e acid phosphate completely, are considered. I n the first experiment four laboratory samples 1 2
Hawaii Agric. Exp. Station, Bull. 41. THISJOURNAL, 9 (1917), 682.
became appreciably warm, and one hour after mixing, the temperatures in Nos. I and z were 3 5 a n d 36' C., respectively, a rise of g and 10' C. over room temperature. At intervals, analyses were made b y the uranium volumetric method for water-soluble phosphoric acid, the results of which are shown in Table I A . This table shows a reversion of from 5.16 t o 5.63 per cent of water-soluble phosphoric acid, and also t h a t the greater reversion is caused b y the greater amount of lime. These points have been laid out diagrammatically on quadrille paper and a smooth line drawn through the points plotted t o show the rapidity with which the action takes place a t first and how i t is gradually retarded. It will be seen t h a t if the lines were extended, considerable time would elapse before all the phosphoric acid would become reverted. While these results were satisfactory, it was deemed advisable t o remove the brown guano as the supply was becoming limited, and t o t r y larger samples over a longer period of time. Some time later, with this in mind, another laboratory experiment was carried on with lime superphosphate, t h e analyses being made a t close intervals
34
T B E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
for about two months, the next analyses after 458 days, and the final complete analyses after 1580 days or approximately 4 years and 5 months. To 1000 g. of acid phosphate in each of two bottles were added 1 5 0 and 300 g. lime, CaO. The analyses of watersoluble phosphoric acid are shown in Table IB. On mixing, the sample with 1 5 per cent lime contained 15.81 per cent water-soluble P205 and 1 7 . 1 8 per cent total PzOa; after standing 1580 days, 0.48 per cent water-soluble, 1 3 . 8 9 available, and 2 0 . 0 2 total PzOa. The sample t o which 3 0 per cent lime was added contained on mixing 1 3 . 0 2 per cent water-soluble PzOs and 14.15 per cent total Pz06; after 1580 days, 2.9 per cent water-soluble, 13.69 per cent available and 1 6 . 6 2 per cent total PZO5. T h e sample containing 1 5 per cent lime shows a
UNFERTILIZED IN FRONT OF STAKE:90 LBS. PER ACRE REVERTED PHOSPHATE AT RIGHT
continued reversion over t h e whole period as was expected, but what was responsible for the irregularity i n t h e sample with 3 0 per cent has not been explained. It will be noticed t h a t some reversion t o tri-calcium phosphate has taken place, b u t the greater part remains as di-calcium phosphate. Since these laboratory experiments indicated in a general way the trend and rate of reaction i t was considered advisable t o continue experimenting on a larger scale under factory conditions. Consequently, t h e following series of experiments were conducted with lots of one ton or more. I n Experiment I , lime and acid phosphate were mixed in a ball mill in proportions of I O parts lime t o go parts acid phosphate. The material after grinding tihrough a coarse screen was caught in bags a n d set out on the floor in order t h a t the reaction could go on t o completion and t h e temperature drop t o t h a t of t h e atmosphere. Experiments 2 , 3 and 4 were conducted in t h e same manner as No. I , t h e only difference being t h a t the proportion of lime t o acid phosphate was increased in each succeeding experiment. The method of handling was not satisfactory, as t h e h e a t and dust soon drove the men away from t h e mill.
Vol.
LO,
No.
I
TABLE 11-FACTORYEXPERIMENT OF MIXINGACIDPHOSPHATE AND LIME MIXTURE Acid PERCENTAGEsLime Phosphate No. 1 10 90 2 15 85 20 80 3 4. 25 75
ANALYSESOF MIXTURR Soluble and Water-Soluble Available P206 P205 19.16 17.61 2.18 18.56 17.16 2.92 17.06 15.71 1.50 16.70 15.33 2.88 ~~
Total
{
PzOs
........ ........
........ .......
Samples for analyses of the first series of experiments with lime and acid phosphate were taken 18 hrs. after mixing. Reaction started from I O t o 2 0 mins. after mixing, and the material lost water rapidly. At the same time i t took on a lighter color and a more friable powdery condition. One-half hour after mixing, the temperature in Nos. I , 2 and 3 was approximately I I O O C., while in No. 4 i t rose t o 1 g o 0 C. The results of this series of experiments are given in Table 11.
UNFERTILIZED AT LEFT: 90 LBS. PER ACRE REVERTED PHOSPHATE AT
RIGHT
The reaction goes on more rapidly as the percentage of lime is increased. The water content of the acid phosphate and also the length of time i t ages in t h e bin before mixing affect t h e rapidity of reaction and intensity of heat generated. Having studied t h e reverting action of lime, our attention was next turned t o carbonate of lime and combinations of carbonate of lime with lime and acid phosphate, t h e object being t o obtain a fertilizer which would contain a considerable part of the phosphoric acid in the reverted form and also t o effect a less dusty mechanical condition. The dusty nature of t h e reverted mixture makes a very difficult a n d disagreeable product t o handle on a large scale. The results of experiments with calcium carbonate (coral sand) and acid phosphate are given in Table 111. It will be noticed t h a t reversion takes place quite rapidly a t first but as the time increases, t h e rate of reversion diminishes. As with lime, the TABLE111-PERCENTAGESWATER-SOLUBLE PZOSIN MIXTURESOF ACID PHOSPHATE AND CORAL SAND ACID PHOSPHATE: 90% 85 %
{ .......................... .....................
MIXTURE cORAL SAND: On mixing.. After 24 hours. 48 hours.. 120 hours 1 1 days..
..................... ....................... ......................
10% 16.3 15.46 15.18 14.44 13.32
r--
15% 15.38 13.04 11.92 11.18 9.68
;IvJ a ,.
14.48 10.98 9.58 8.86 8.2
Jan., 1918
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
reversion increases with increasing proportions of carbonate of lime. With the carbonate of lime, however, there is very little rise in temperature. It is unfortunate t h a t only the water-soluble phosphoric acid determinations were made on this series of experiments, as a comparison of the soluble and available would have been valuable and interesting. I n a n endeavor t o get more satisfactory results with lime and acid phosphate on a factory scale, mixtures of go per cent acid phosphate and I O per cent lime, and also 85 per cent acid phosphate with 15 per cent lime were again ground together in a ball mill. These mixtures were allowed t o cool and after 2 4 hrs. samples were taken for analyses. T h e mixtures were sampled again after one week. TABLEIV-MIXTURES OB ACID PHOSPHATE AND LIME 907 ACID 8 5 7 ACID PHOSPHAT; & 10% LIME P H O S P H A& T ~15% LIME Soluble Soluble Waterand Waterand PER CENT ~ 2 0 s soluble Available TOTAL Soluble Available TOTAL After standing 17.56 19.1 19.42 None 24 hours., . 3.03 18.50 16.55 18.64 19.28 None 1 week 1.66 17.97
{
.....
The reversion here was quite complete and little if any of the acid phosphate was changed t o the tricalcium form. The appearance of t h e material was quite similar t o precipitated phosphate. It was found impractical t o work this material through a ball mill, however, on account of the gradual accumulation of the mixture in t h e mill and also the heat generated by the reaction. A similar experiment was then undertaken with mixtures of acid phosphate, lime and coral sand with the object of obtaining the same result: i. e., a reverted phosphate, but with the idea of retarding and tempering the violence of the reaction. The limited capacity of the ball mill and its tendency t o choke and t o accumulate heat led us t o run the remaining tests through a cage disintegrator. The reversion which took place in this material is shown in Table V.
35
AGRICULTURAL E X P E R I M E N T S
With regard t o the effect of reverted phosphate on growing crops, and also its commercial value, there are differences of opinion. I n 1914 the state chemists of North Carolina, South Carolina, Alabama, Mississippi and Georgia were all opposed t o a reverted phosphate. Dr. Cameron, then of t h e Bureau of Soils a t Washington, is also quoted as not favoring lime being mixed with superphospha.tes. Possibly in the majority of cases the water-soluble phosphate is the one used. There are exceptions, however, and we have found in nw.merous cases t h a t the reverted phosphate is just as valuable or even more valuable t h a n the water-soluble when applied t o cane upon upland soils. These !;oils are, as a rule, highly ferruginous clays. On soils which have not been cropped for several years, the reverted phosphate gives excellent results. The accompanying photographs show the difference between cane unfertilized and t h a t receiving per acre go Ibs. of phosphoric acid in reverted form. I n the check plot t h e canes per stool ranged from 5 t o g while in the reverted phosphate plot the variation was from g t o 15. These photographs were taken in a series of experiments run by the Hawaiian Sugar Planters' Experiment Station, on land of the Oahu Sugar Co. Experiments made b y the U. S. Agricultural Experiment Station' upon rice, also show favorable results from reverted phosphate, particularly the Gold Seed rice which has a long growing period. A gain of 13 2 per cent over t h e check plot is recorded. I n view of these results and the fact t h a t the reverted form is preferred by certain growers t o any other, it would seem t h a t the practice of condemning or setting arbitrarily a lower value on reverted phosphate is open t o criticism. Credit is due and acknowledgment hereby made to
H. M. McCance for aid in the analytical work reported in this paper.
TABLE 'V-EXPERIMENT WITH ACID PHOSPHATE, LIME AND CALCIUM CARBONATE 8 0 7 ACIDPHOSPHATS MIXTURs: ' 85 % ACIDPHOSPHATE 15%"CaCOz 5 % CaO 10% CaCOa 5 % CaO Water- Soluble and Water- Soluble and Available TOTAL Soluble Available TOTAL PERCENT PtOs: Soluble After standing 24 hours.. 4.94 3.26 ... 10 days.. , 4.52 i+:k 2.42 14.77 K48
{
+
PACIFIC GUANO& FERTILIZER COMPANY HONOLULU. HAWAII
+
. .. . . . ..
The disintegrator makes a sufficiently homogeneous mixture which passes rapidly through the machine, and which is discharged almost before reaction begins. Reaction attains its height about 30 minutes after leaving the disintegrator, which allows sufficient time for handling. The heat generated removes excess of moisture, causing a loss in weight of about 5 per cent and leaving a free, dry powder, the phosphoric acid of which consists mainly of di-calcium phosphate. Thus with a 40-in. cage disintegrator, from 20 t o 2 5 tons per hour may be mixed direct into containers, doing away with the handling of a very dusty material, and avoiding excessively high temperatures.
ELECTRIC FURNACE SMELTING OF PHOSPHATE ROCK AND USE OF THE COTTRELL PRECIPITATOR IN COLLECTING THE VOLATILIZED PHOSPHORIC ACID By J. N. CAROTHERS Received October 8, 191'7
The work described in this article is a continuation, on a commercial scale, of pqeliminary work which was carried on more than a year ago. I n the preliminary work,2 furnace operation was not continuous for a period of days, consequently no conclusion could be drawn a s t o cost of installation and operation. The work of these later tests was made possible only by the cobperation of the Bureau of Soils with several 1 3
Hawaii Experiment Station Report 1907-1908. THISJOURNAL, 9 (1917), 26.
