T H 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 Along this same topic, it is a very wise precaution to use great care in admitting the liquor from each body to the succeeding one. If it is simply allowed t o enter into the bottom below the tube sheet, the “flash” will be local, causing the tubes in the immediate vicinity to spout violently, projecting liquor t o the dome. The proper remedy is t o distribute this feed in the bottom by means of a perforated coil or manifold, or if this is not used, t o provide a flush pot or recipient on the outside of the evaporator, with the upper part connecting with the vapor belt and the lower part with the bottom. Still another way is to use a spray pipe above the tube sheet, and still another is t o feed from above with the pipe extending t o the center, the opening facing downward. Many have the tendency to make small of this problem, but when it is recalled that enormous quantities are treated in a given time, it will be found that the game is well worth the candle. For instance, a loss of ‘/4 per cent in the evaporator contemplated above would amount t o about Boo lbs. of sugar per day, worth, on a six cent basis, $48, and in a campaign of one hundred and twenty working days, this would be $5760, which justifies almost any kind of provision to recover it. And yet there are many evaporators which lose more than l/4 per cent, but the man who owns it does not know, for evidently the loss is greatest in the last body when the vapor goes into the condenser, and in so doing is diluted about 30 to I . E. B. BADGER & SONSCOMPANY BOSTON,MASS.
NOTES ON THE ANALYSIS OF MOLASSES By HERBERTS. WALKER Received January 11, 1918
I n comparing the results of a large number of determinations of sucrose in final molasses analyzed by students a t the College of Hawaii and by myself, I have noticed that the same sample of molasses appears to contain from 0.5 per cent t o 1.0 per cent less sucrose if clarified with dry lead subacetate than if the lead subacetate solution is used. These discrepancies were a t first attributed t o personal errors, but as the differences invariably persisted in the same direction, an attempt was made t o trace out their causes and ascertain which, if either, of the two methods of clarification could be relied upon. The method of clarification by lead subacetate solution used in this laboratory is that prescribed by the Hawaiian Chemists’ Association. 3 5.75 g. molasses are dissolved in water, clarified with 40 cc. of a solution of basic lead acetate of 54’ Brix, made up to 2 j 0 cc. with water and filtered. 50 cc. of the filtrate are treated with I cc. of a saturated solution of aluminum sulfate, made up to 5 5 cc. with water and filtered. Reading (in a 2 0 0 mm. tube) multiplied by 2 gives the direct polarization. 7 5 cc. of the original filtrate are inverted by the Herzfeld method and made up t o I I O cc. Reading multiplied by 8/3 is the invert polarization. The factor used is 1 4 2 - o.5t. For clarification with dry lead subacetate a method derived from that proposed by Cross and Taggartl 1
Louisiana Bulletin 136.
Vol.
IO,
No. 3
has been tried. 35.75 g. molasses were dissolved in water and made up t o 250 cc., then clarified with 1 2 t o 1 5 g. dry basic lead acetate and filtered. About 5 0 cc. of the filtrate were de-leaded and made slightly acid by the addition of 0.3 g. dry powdered sodium bisulfite and filtered for direct polarization. 7 5 cc. of the original filtrate were inverted and made up as in the previous method for invert polarization. Since. the same concentrations of molasses and of lead subacetate were used in both methods, the direct polarizations were both made in a slightly acid solution and the inversion procedure was identical, i t follows t h a t the difference in results must have been due either t o the volume occupied by the lead precipitate causing too high results in the ‘(wet” method, or t o the dilution in the “dry” method produced by an excess of lead going into solution over that required t o precipitate impurities, which would tend t o yield too low figures. VOLUME OCCUPIED B Y T H E LEAD PRECIPITATE
35.7 5 g. of a waste molasses were dissolved in water, clarified with 40 cc. lead subacetate solution and the precipitate washed by decantation during a period of several days until the clear decantate from four consecutive washings showed no polarization in a 400 mm. tube. This sugar-free lead precipitate was transferred t o a 2 5 0 cc. flask together with 2 2 g. granulated sugar, made up t o the mark with water and polarized in a 400 mm. tube, giving R = 68.36. 2 2 g. of the same sugar made up with water alone in the same flask read 67.46. The difference of 0.90 or 1.33 per cent of the total polarization could have been caused only by t h e volume occupied by the lead precipitate. The volume left in the flask for the solution in this case must have
X 67‘46 -~ - 2 4 6 . 7 2 cc. The 68.36 precipitate itself then occupied 3 . 2 8 cc. The sugarfree lead precipitate from another 35.75 g. sample of this same molasses was placed in a 2 5 0 cc. flask with 3 2 . 5 0 g. granulated sugar, made up to the mark with water, filtered and polarized in a 400 mm. tube, giving R = 101.20. The same weight of sugar dissolved in The presence of the 2 5 0 cc. water alone read 99.80. lead precipitate caused an increase of 1.40 per cent of the total polarization. If the molasses from which this precipitate was made contained say 35 per cent sucrose, its apparent value would be increased by 35 X 0.014, = 0.49 per cent sucrose. The washed lead precipitate from 35.75 g. of molasses from another plantation was still more voluminous. Duplicate tests on it were as follows:
been not
250
cc., but
250
READING 99.74 99.83 32.50 g. sugar made up to 250 cc. with water alone.. 32.50 g . sugar made up to 250 cc. with lead precipitate and water .. . 101.63 101.87
. .... .. ............. . ... .. .. ...... .. .. ........ . . . . -2 . OB Increase due to lead precipitate.. , . . . . . , . . . , . . . . . . . . . . . 1.89
..................
AVERAGE
1.96
If this molasses contained 3 5 per cent sucrose it would appear t o contain 35.69 per cent if analyzed by t h e H. C. A. method, providing there were no other errors in the method.
Mar., 1918
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
DILUTION
BY
DRY
LEAD
SUBACETATE
A solution of refined sugar containing 1 3 g. per I O O cc. polarized in a 400 mm. tube 99.51. To a portion of this solution was added dry basic lead acetate in the proportion of 3 g. per I O O cc. The filtered solution then polarized 98.99, a drop of 0.52 per cent. To obtain the maximum clarification of a half-normal molasses solution, u p t o 6 g. lead per I O O cc. may be required. Assuming that half the lead goes into solution withopt being precipitated, a molasses containing 3 5 per cent sucrose might suffer an apparent loss of 3 5 x 0.0052 = 0.18 per cent sucrose on account of this dilution. E X P E R I M E N T S W I T H ARTIFICIAL MOLASSES
The great difficulty in testing a method for the determination of sucrose in molasses is of course due t o the fact t h a t we cannot know exactly how much sucrose there really is in the molasses. If i t were possible t o remove all the sucrose from a molasses without disturbing its other constituents, i t would be a simple matter t o make u p standard samples for testing out new methods. An attempt in part t o accomplish this was made by dissolving I kg. of molasses in I O liters water, clarifying with I liter basic lead acetate solution and washing the precipitate b y decantation until free from polarization. The lead precipitate was then decomposed by hydrogen sulfide, the lead sulfide filtered off and the clear solution evaporated t o about I liter, yielding a concentrated solution containing most of the lead-precipitable impurities of the original molasses. 50 cc. of this “impurities” solution were found t o require about 40 cc. basic lead acetate for complete precipitation and therefore represent roughly the precipitable impurities in a 3 5.7 j g. sample of molasses. j o cc. of “impurities” alone analyzed by the H. C. A. method gave a direct polarization of -0.55, an invert and “sucrose” -0.02, or pracpolarization of -0.57 tically nothing. 1 2 g. pure sucrose alone, analyzed by the H. C. A. method for sucrose in final molasses but omitting clarification and de-leading, indicated 33.59 per cent sucrose 12.0 (based on a 3 5 . 7 5 g. sample) as against -- or 33.56 35.75 per cent actually present. 1 2 g. pure sucrose mixed with 50 cc. “impurities” and analyzed b y the H. C. A. method indicated 34.15 per cent sucrose, or 0.59 per cent too much. 1 2 g. pure sucrose mixed with 50 cc. “impurities” and analyzed by the dry lead method, using 1 5 g. dry lead subacetate instead of 40 cc. of the solution, indicated 33.28 per cent sucrose, or 0.28 per cent too little. T H E E F F E C T OF I N V E R T SUGAR
Much has been written concerning the influence of the invert sugar in cane molasses on the Clerget determination and the necessity for making direct and invert polarizations in solutions of the same acidity. I have made numerous experiments with many different acids and acid salts in a vain endeavor to find some concentration or combination of a weak acid which would cause invert sugar t o polarize as strongly t o the le€t as does j cc. of concentrated HC1 per I O O cc.
I99
solution, and still not cause any inversion of sucrose during the I 5 min. or more required t o filter and polarize a molasses solution. Fortunately the error introduced in cane molasses analysis is not as large as might be supposed from the amount of time and labor spent in attempting its correction. The invert sugar resulting from the inversion of a normal weight of sucrose in I O O cc. has a minus polarization of about 31.7 a t 20’ C., in neutral solution, while the same weight of invert sugar in a solution containing 5 cc. concentrated HCl per 100 cc. reads 32.7 t o the left, t h e increased reading due t o acid being 1.0in 31.7, or 3.2 per cent of the total minus polarization. The amount of invert sugar present in cane molasses, calculated from average differences between direct polarizations and sucrose values, has a total minus polarization of from about 3 t o 5, so t h a t we should expect a n increase in acid over neutral reading of from -0.1 t o -0.16, indicating a fictitious increase in sucrose in the final calculation of about 0.1 per cent when direct polarizations are made in neutral or weakly acid solution and invert readings are taken in a solution containing 5 g. HC1 per IOO cc. Of course, if direct readings are made in alkaline solution this error may be largely increased. To test the above theory, a neutral solution of invert sugar was prepared, containing about 24 g. per I O O cc. 2 5 cc. of this, containing somewhere near the amount of invert sugar ordinarily present in 35.75 g. waste molasses, were analyzed in duplicate b y the H. C . A. method for sucrose (omitting clarification and subsequent de-leading) with the following results:
. . , , . . . .. . . . . . . . . ... . . . . . . . . . . . . . .. . . . . . . . . . . . . . . , . . . . . .
Direct polarization in neutral solution. Polarization after inversion (25.6’ C.). “Sucrose”. ,. , ,
0.14%
0. 12T0
On two more samples the direct as well as the invert reading was made in a solution containing 5 cc. concentrated HCl per I O O cc. and gave the following results : Direct polarization.. . . . . , . . . , . . . . . , , , , , -4.63 -4.65
. . . . . . . . , . . . -4.62 . . . .. . .. . . . . . . . . . , . , . . . . -0.01
Polarization after inversion., “Sucrose”. , , , ,
-4.61 -0.04
This proves the absence of sucrose in the invert sugar solution and gives a n idea of the magnitude of the error introduced by making direct readings in neutral instead of acid solution. 1 2 g. pure sucrose together with approximately 6 g. invert sugar were next analyzed by the H.C. A. method. The readings (based on. a 35.75 g. sample) were: Direct 28.94, Invert (at 24.6’) -14.76, “S~crose’~ 33.68 per cent against 33.56 per cent actually present. The error involved appears t o be in the neighborhood of 0.1 per cent sucrose, which is well within the limit of personal error of most analysts. ANALYSES O F RECONSTRUCTED MOLASSES
A mixture of 1 2 g. sucrose, 6 g. invert sugar and 50 cc. “impurities” was analyzed by the H. C. A. method. The readings on two separate samples were 29.70 29.79 Direct., . . . . , . , , . . . . . , . . . . . . . . . . -14.83 -14.73 . . . . . 24.7’ 24.7’ Temperature.. . 34.26% 34.34 per cent sucrose
200
T H 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
A mixture of 1 2 g. sucrose, 6 g. invert sugar and 5 0 cc. “impurities” analyzed by the dry lead method ( I S g. dry lead subacetate) read
Vol.
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No. 3
The method of clarification with basic lead acetate solution, when worked on a reconstructed molasses of a known sucrose content, is thus found t o yield results in this particular case 0.68 per cent too high, while clarification with the dry subacetate gave a figure 0.09 per cent too low. While the dry lead method previously described has been shown t o give fairly accurate results on known mixtures, due in part t o compensating errors, it still suffers from the disadvantage t h a t a large excess of lead which is sometimes necessary for clarifying dark colored products causes low results on account of the dilution which i t produces. Extreme care must also be taken t o add just the proper amount of de-leading agent. Too little of this may cause too high a direct polarization, while any excess over t h a t required for precipitation of the lead introduces a still further dilution of the solution. Especial care is needed when sodium bisulfite is used for de-leading ; subsequent experiments have caused me t o abandon this reagent altogether in sugar analysis, owing t o the marked specific effect i t has on the rotation of glucose. To obviate some of these difficulties the following modification of the dry lead method for final molasses has been evolved, and is submitted for trial and criticism.
sates for the dilution caused b y any excess lead originally dissolved. A pale yellow filtrate results which can be read with ease in a 400 mm. tube, so there need be no multiplication of the reading error. The concentration of phosphoric acid selected ( 2 g. per IOO cc. solution) is based on a number of tests made t o determine the maximum acidity possible without danger of inversion. While this amount of phosphoric acid does not, in pure solution, produce quite as high a left rotation of invert sugar as does j cc. of concentrated HC1, yet, under working conditions of analysis, the difference is so slight as t o introduce practically no error. A number of different acids were tried out in this connection, but none was found to be as generally satisfactory as phosphoric. Sulfurous acid in a concentration of 50 cc. of the saturated solution per IOO cc. total solution causes approximately as high a rotation of invert sugar as does 5 cc. of concentrated HC1; in fact, if sodium salts are also present, the left rotation of invert sugar may become appreciably greater in sulfurous t h a n in hydrochloric acid solution, due not t o a n increase in t h e polarization of fructose b u t t o a depressing effect on the rotation of glucose. Moreover, a molasses solution containing sulfurous acid of this concentration is not absolutely free from danger of inversion a t tropical laboratory temperatures. I have found a loss in direct polarization of approximately 0.5 per cent sucrose in one hour a t 2 6 ’ C. Owing t o the finely divided condition of the lead sulfite precipit a t e a very considerable time often elapses between the addition of sulfurous acid and t h e direct reading, so this chance of error, while not very great, is worthy of note.
N E W PROCEDURE FOR D R Y LEAD CLARIFICATION
TESTS OF T H E N E W D R Y LEAD METHOD
...................
Direct.. 29.17 29.24 Invert -14.15 -14.15 Temperature.. 25.0’ 25.0’ “Sucrose”. ................. 33.44% 33.50% AVERAGB. 33.47 per cent sucrose
.................... ..............
.............
Dissolve a double normal weight of molasses ( 5 2 g.) in water and make u p t o 300 cc. Clarify in a larger flask with 1 5 t o 20 g. dry lead subacetate and a few grams of dry sand and filter. To 7 5 cc. of the filtrate in a IOO cc. flask add 2 0 cc. of a solution containing IOO g. phosphoric acid per liter, make up t o I O O cc. with water and filter. (The addition of half a gram or SO of zinc dust just before filtration, while not usually necessary, lightens up the color of the solution perceptibly and has no effect on t h e polarization.) Reading in 400 mm. tube = direct polarization (D). Take another 7 5 cc. portion of the original filtrate in a IOO cc. flask, add z cc. dilute HC1 ( I volume concentrated acid t o I volume water) t o neutralize the alkalinity due t o excess of lead subacetate, heat t o 65’-70’ C., a d d I O cc. HC1 (I t o I), let stand in air 1 5 min. or more, cool t o room temperature, make up t o IOO cc., add zinc dust in slight excess and filter. Reading in 400 mm. tube = invert polarization (I). Then D-I Sucrose = 142.1- o.5t’ This method has several apparent advantages over ordinary dry lead clarification of molasses. The addition of a moderate excess of phosphoric acid t o a portion of the first filtrate before making u p again t o a definite volume throws down all the lead as a voluminous, easily filtered precipitate whose volume compen-
CORRECTION O F DILUTION ERROR
To 500 cc. of a half-normal solution of refined sugar 1 5 g. dry lead subacetate were added. 7 5 cc. of t h e resulting solution were made up t o IOO cc. with water, filtered and polarized in a 400 mm. tube, giving R = 74.24. To another 7 5 cc. portion I cc. of a jo per cent solution of phosphoric acid was added t o completely precipitate the lead, the solution then made u p t o IOO cc. with water, filtered and polarized in a 400 mm. tube, giving R = 74.53. The original solution, before adding lead, polarized 99-51, corresponding t o 74.63 if diluted from 75 t o IOO cc. The loss i n polarization caused b y a very considerable dilution by dissolved lead is thus very nearly if not quite restored by precipitating the lead from a definite volume of solution and then making up with water t o another definite volume, the theory being t h a t t h e volume occupied by the lead phosphate precipitate is practically the same as t h e increased volume caused by solution of lead acetate. TESTS WITH ARTIFICIAL MOLASSES
A solution of lead-precipitable impurities was made by dissolving I kg. of waste molasses in 40 liters water, precipitating with 2 liters lead subacetate solution, washing free from polarization, decomposing the lead precipitate with H2S, filtering and evaporating t h e filtrate t o about 2 kg. I O O cc. of this solution required about
Mar., .rg18
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
40 cc. basic lead acetate solution for complete precipitation. A Clerget determination on this solution of impurities showed: Direct polarization = -0.02, Invert polarization = 0.00. 1 2 g. “Domino” sugar and IOO cc. “impurities” were analyzed by the H. C. A. method and gave D = 34.05, I (27.2’ C.) = -9.64, “Sucrose” = 34.05 (based on a 35.75 g. sample). 17.455 g. “Domino” sugar and 1 5 0 cc. “impurities” were made up with water t o 300 cc. and analyzed by t h e new dry lead method, using I j g. dry lead. The results were D = 33.58, I (27.3’ C.)= -9.51, “Sucrose” = 33.54 (based on a 5 2 g. sample). The sucrose actually present in each case was 33.55 per cent. INVERT SUGAR A N D “IMPURITIES” WITHOUT SUCROSE
Samples were prepared containing approximately the amounts of “impurities” and invert sugar found i n cane molasses (about 1 7 per cent invert sugar) and analyzed for sucrose by three different methods with the following results: METHOD D H.C. A . . ...............-3.67 Sulfurous Acid.. ......... -3.66 Dry Lead.. -3.42
.............
I -3.74 -3.52 -3.42
“Sucrose” 0.05 -0.11 0.00
S U C R O S E , I N V E R T S U G A R A N D “IMPURITIES” 1 2 g. “Domino” sugar, I O O cc. “impurities” and about 6 g. invert sugar were analyzed by the H. C. A. method and gave D = 30.20, I ( 2 7 . 0 ~ C.) = -13.58, ‘Lsucrose” = 34.07 per cent. 17.455 g. “Domino” sugar, 1 5 0 cc. impurities and about g g. invert sugar were analyzed by the new dry lead method, using 18 g. lead subacetate and gave D = 30.01,I ( 2 6 . 8 ” C.) = -13.27, “Sucrose” = 33.63 per cent. Sucrose actually present in each case = 33.55 per cent. The H. C. A. result was therefore 0.52 per cent too high, while t h a t of the dry lead method was 0.08 too high, or practically correct within the limit of experimental error, though a rather large excess of dry lead was used for clarification. For comparison, 20.142 g. “Domino” sugar (representing 33.55 per cent sucrose on a 60 g. sample), 1 7 0 cc. “impurities,” but no invert sugar, were clarified with 60 cc. lead acetate solution in a 300 cc. flask and analyzed by Pellet’s sulfurous acid method.’ The results were: D = 34.11, I (26.9”C.)= - 9 . 5 8 , “Sucrose” = 33.99 per cent. E F F E C T OF VARYING A N O U N T S OF DRY L E A D
5 2 X 10/3 = 173.33 g. of a waste molasses were dissolved in water and made up t o I liter. Three portions of this were clarified separately with dry lead subacetate corresponding t o IO, 2 0 and 3 0 g., respectively, per 300 cc. and analyzed as usual, except t h a t in deleading, the amount of phosphoric acid used was varied according t o the amount of lead, 3, 4 and 5 cc., respectively, of a 50 per cent solution being used. Lead subacetate to 300 cc. solution 10 g. 20 g. 30 g. 1
D 34.45 35.02 35.71
I -15.18 -14.47 -13.90
Pellet, Intern. Sugar J . , 1913, 424.
i
27.3’ 27.3’ 27.1’
“Sucrose” Per cent 38.64 38.53 38.59
201
Increasing the amount of lead u p t o double t h a t required for efficient clarification has no effect on the sucrose value. For comparison, this same molasses was analyzed b y the H. C. A. method, using varying amounts of lead subacetate solution and correspondingly varying amounts of aluminum sulfate for de-leading. Lead subacetate for 35.75 g . molasses in 250 cc. solution D 20 cc. 35.05 30 cc. 35.27 40 cc. 35.56 50 cc. 36.08 50 CC.(Q) 36.01 70 cc. 37.10 (Q) Sulfurous acid method.
I -15.48 -15.25 -14.88 -14.57 -14.64 -14.02
1
26.4’ 26.2’ 26.5’ 26.2’ 25.9’ 26.1’
“Sucrose” Per cent 39.23 39.19 39.18 39.30 39.25 39.64
Within reasonable limits the sucrose indicated by this method is independent of the amount of lead used for clarification, but taking the new dry lead method t o be correct, the H. C. A. method yields results averaging about 0.7 per cent too high. It will be noted t h a t practically no improvement in this respect results from making the direct polarization in a solution strongly acid with sulfurous acid. This is t o be expected, since the principal error, t h a t due t o the volume of the lead precipitate, remains the same. D E T E R M I N A T I O N O F BRIX, S U C R O S E A N D P U R I T Y I N T H E S A M E SOLUTION
The dry lead method lends itself readily to the determination of gravity solids and sucrose in the same weighed sample of molasses. As these determinations are both required, some time may be saved by not having t o weigh out separate samples for each. The only extra operation involved is t o weigh the molasses solution after making i t up t o 300 cc. preparatory t o clarifying. Knowing the water capacity of the flask a t standard temperature, the specific gravity and thence the Brix of the molasses can readily be calculated. For this method i t is sometimes more convenient t o take 86.67 g. molasses in 500 cc. instead of 52 g. in 3 0 0 cc. ‘ An alternate method for making the two determinations on the same sample is t o prepare a large sample of molasses diluted with 5 times its weight of water, determine Brix on a portion of it and clarify another portion with dry lead subacetate for the sucrose determination. The sucrose is gotten from special tables1 or from the formula ’ Sucrose = R X
26.121
x
sp. gr. a t 27.5OC. An example of each of the above determinations f 0110 ws : IOO
1-86.67 g. molasses were dissolved in water and made up to 500 cc. Weight of solution a t 26.3’ = 528.75 g. Water capacity of the flask at 27.5’ = 497.88 g . 528.75 Sp. gr. of solution = 497.88 = 1.0620 = 15.28 Brix = 15.19 Brix cor-
-
rected for temperature. 528.75 15.19 X = 92.68 Brix of original molasses.
86.67
The 500 cc. molasses solution after weighing were clarified with 30 g. dry lead subacetate and on analysis gave the following results: D = 34.96, I (26.3”) = -14.94, Sucrose = 38.70, Gravity purity 41.65. 1 Hawaiian Chemists’ Association, “Methods of Chemical Control,’’ Table 4.
-
202
11-A
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
second sample was diluted with 5 times its weight of water. Brix of diluted molasses by pycnometer at 26.2' C. = 15.51. Brix corrected = 15.42. Brix original = 6 X 15.42 = 92.52. 500 cc. of this diluted molasses were clarified with 30 g. dry lead and gave, when analyzed, the following results: Direct reading (400 mm. tube) = 35.53. Invert reading (26.3' C.) = -15.17. Clerget reading = 39.32. Sucrose (from tables) = 9.66. Sucrose in original molasses = 9.66 X 6 X 4/a X 2 0 0 / 4 0 0 38.64 per cent. Gravity purity = 41.73.
-
S U M MARY
I n a n attempt to explain the discrepancies in results obtained in Clerget sucrose determinations in waste molasses, a large amount of experimental evidence indicates t h a t the method of clarification with lead subacetate solution as recommended b y the Hawaiian Chemists' Association yields results from 0.5 t o 0.7 per cent too high, this being mostly due t o t h e large volume occupied b y the lead precipitate. Clarification with dry lead subacetate gives figures more nearly approaching the true sucrose content of the molasses, but is apt t o run a little low, especially if a n excess of lead is used in clarifying. A modification of the dry lead method t o overcome the dilution error is suggested, and experimental proof of its correctness is offered. COLLEGE OF HAWAII DEPARTMENT O F SUGAR TECHNOLOQY HONOLULU, HAWAII
RELATION BETWEEN EFFICIENCY OF REFRIGERATING PLANTS AND THE PURITY OF THEIR AMMONIA CHARGE' B y F . W. FRERICHS Received January 5 . 1918
Since writing this paper several months ago a singular case of unpreparedness has developed in t h e ammonia trade. As you all know, most ammonia is obtained as a byproduct from gas works and from coke oven plants. I n gas works and in the older coke oven plants the ammonia is obtained b y scrubbing the gas with water and recovering the ammonia from the diluted gas liquor by distillation, whereby free ammonia is obtained, which may be used in the manufacture of aqua and anhydrous ammonia and ammonium salts. I n the more modern coke oven plants the so-called direct process is employed in which only so much ammonia is obtained in the form of ammoniacal liquor as condenses with the water distilling from t h e carbonized coal. This amounts t o only about 2 0 per cent of the total ammonia. The remaining 80 per cent is obtained by washing the gas with a slightly acid solution of sulfate of ammonium in small apparatus. These plants produce therefore a large amount of sulfate of ammonium, and they are not provided with scrubbers by the use of which all ammonia might be obtained as ammoniacal liquor. This was desirable in peace times because the larger part of ammonium salts was used in the fertilizer trade in the form of sulfate of ammonium. But when the war demanded ever-increasing quantities of nitrate of ammonium for explosives, the am1 Paper read at the 10th Annual Meeting of the American Institute of Chemical Engineers, St. Louis, Mo., December 5-8, 1917.
Vol.
TO,
No. 3
moniacal liquors were insufficient in quantity; and although much sulfate of ammonium was available, there was only one plant in the United States in which aqua ammonia could be made from sulfate, and this plant was entirely engaged in the manufacture of ammonia for the refrigerating industry. And i t had become necessary t o reconstruct this one plant t o adapt i t t o the use of crude ammoniacal liquor on account of the high price demanded by sulfate of ammonium during the war. Upon request of the Food Administration of the United States, remodeling of the plant was temporarily abandoned and even a 5 0 per cent increase in capacity of the sulfate plant was agreed t o for the purpose of securing ample supply for cold storage warehouses and ice plants, the Government aiding in obtaining a supply of sulfate of ammonium a t reasonable cost. After this was arranged there arose a sudden and large demand for ammonia for the manufacture of nitrate of ammonium, and sulfate of ammonium being the only available material, it had t o be manufactured from this ammonium salt. There exists the singular condition t h a t we have coking plants which are prepared t o make much sulfate, but which can make only a limited amount of ammoniacal liquor; and we have nitrate of ammonium plants which can work ammoniacal liquor, b u t which cannot make nitrate of ammonium from sulfate. We have ample ammonia material, but we are utterly unprepared t o make nitrate of ammonium from it. It is known t h a t in England nitrate of ammonium is made by double decomposition of sulfate of ammonium and nitrate of sodium, but it is understood t h a t in this process about 20 per cent of the ammonia is wasted. To investigate this process a Commission went t o England several weeks ago, and their report by cable is expected now. But even in the case of a favorable report, it is estimated t h a t i t will require six months before works of sufficient size can be put into operation. Being familiar with t h e manufacture of ammonia from sulfate, I was called t o Washington t o consult with officials of the War Department. Complete plans, patterns, assistance, a n d patent rights were promptly offered and accepted for the purpose of erecting new plants, each the size of our St. Louis plant, a number of which are contemplated for the various explosive works. We have the singular opportunity of witnessing unprecedented growth of a n industry which (economically speaking) has outlived its usefulness, and which after t h e war must die out, being unprofitable under peace conditions. Reconstruction of our St. Louis plant is being carried on under great difficulties and I must ask your indulgence if I show you this afternoon a sadly disarranged plant, which must be operated while i t is being reconstructed. I had hoped t o have the plant finished for this convention, but Government demands changed the plans, and if I wish t o keep my promise t o you I must show the works as they are now. The scarcity of ammonia is unprecedented and the importance of saving ammonia has become para-
