Oct.,
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
1920
APPLICATION T O STORAGE F R U I T
Now, what changes can be expected in fruit first frozen in cold storage and then subjected t o t h e foregoing methods of analysis? Evidently changes brought about by freezing in storage will n o t be repeated b y a laboratory freezing, provided t h e first freezing was thorough and the laboratory freezing was not delayed too long. This was found t o be the case with peaches alleged t o have been frozen in storage, manifesting obvious characteristics of frozen peaches, and analyzed within a week after removal from cold storage (Table IV). SOLD c - S a m p l e TION (1) (2)
AVERAGE
TABLE IV Invert
Sucrose
Ratio
Percentage Inversion
Here only 1.26 per cent of inversion was obtained in -the peaches by a laboratory freezing. Now, since unfrozen peaches (Tables I1 and 111) gave much inversion b y laboratory freezing, i t may be concluded t h a t t h e fruit analyzed in Table I V had previously been frozen in storage. I n this connection i t may be observed t h a t not only is sucrose inverted during ripening, over-ripening, rotting, a n d freezing, b u t invert sugar, previously present or formed b y inversion, m a y be lost by chemical decomposition, or by t h e metabolism of t h e p l a n t , or by rotting organisms, such as yeast or molds. This is illustrated by t h e following d a t a obtained from peaches (Table IV) after they had been kept out of cold storage for one month and had become completely covered with mold. SOLU-r-SarnpleTION
(1)
(2)
TABLE V AVERAGE Invert Sucrose
Ratio
Percentage Inversion
It must be concluded t h a t mold consumed a large part of t h e invert sugar, or a t least t h a t it consumed invert sugar more rapidly t h a n i t did sucrose. Therefore too great deterioration of fruit out of effective cold storage will invalidate t h e chemical detection of a prior frozen condition. SUMMARY
The advantages of t h e method herein described are: I-Advantage is taken of divergencies in t h e largest components of t h e fruit 2-Inversion subtracts from t h e sucrose concentration a n d adds t o t h e invert sugar concentration, thus giving accurate measurements of such divergencies. 3-Accurate gravimetric measurements are made by standard methods. THE DETERMINATION OF MOISTURE IN BEET-SUGAR FACTORY PRODUCTS' By V. L. Aikin GREATWESTERNSUGAR COMPANY, FORTCOLLINS,COL.
The problem of obtaining t h e correct moisture cont e n t of various saccharine products is as important t o 1 Presented at t h e 59th Meeting of t h e American Chemical Society, Si. Louis, M o , April 1 2 to 16, 1 9 2 0
979
the sugar laboratory chemist as is t h e knowledge of how t o obtain correct d a t a on t h e percentage of sugar or other constituents. He finds very definite and proved methods for t h e determination of sugar, alkalinity, ash, etc., in a n y standard reference book, but the literature is lacking in uniformity in regard t o methods t h a t prove experimentally t o give correct results €or t h e percentage of moisture. A C C E P T E D METHODS F O R M O I S T U R E D E T E R M I N A T I O N
T h e report of t h e editing committee of t h e Association of Official Agricultural Chemists gives t h e following method for t h e determination of moisture in massecuites, molasses, a n d other liquid and se*mmiliquid saccharine products. D R Y I N G Oh' QUARTZ SAND-Digest pure quartz sand with strong hydrochloric acid, wash, dry, ignite, and preserve in a stoppered bottle. Place 6 t o 7 g. of the prepared sand and a short stirring rod in a flat-bottomed dish, d r y thoroughly, cool in a desiccator, and weigh. Add 3 t o 4 g. of molasses, mix with the sand (if necessary, add a little water to incorporate t h e t w o thoroughly), d r y in a water oven a t t h e temperature of boiling water for 8 t o IO hrs., stirring a t intervals of a n hour, cool in a desiccator. and weigh. Stir, heat again for a n hour, cool, and weigh; repeat t h e heating and weighing until the loss of water in an hour is not greater t h a n 3 mg. Pellet recommends t h a t t h e material be mixed with pumice stone and dried a t 1 c 2 O t o 105' C. G E R M A N O F F I C I A L METHODS. T H I C K JUICE-A ratio of 2 5 parts of iron-free sand to one part of d r y substance is sufficient. Three grams of thick juice t o 50 g. of iron-free sand are weighed 3ut. The drying takes place in vacuo a t 1 0 j O t o 110' C. MASSECUITES-TWO t o three grams of massecuite are intimately mixed with 50 g. of iron-free sand in a moisture dish, and given a preliminary drying for a quarter of an hour in a drying oven a t 70° C. After again thoroughly mixing, the drying is continued for 6 t o 8 hrs. a t 10.5' t o 110' C. in a vacuum oven or air bath. The weight is taken as constant when, after repeating t h e drying for a period of 2 hrs., t h e loss in weight is less t h a n 0.1per cent. PRESENT INVESTIGATIONS
Several years ago t h e writer did some work 011 methods for moisture determinations in beet-sugar factory products, and t h e results are submitted i n the hope t h a t they may furnish some information on the various factors influencing t h e determination of moisture. As molasses is one of the most impure products with which we have t o deal, it was used as a basis for most of t h e work, a n d t h e results were checked on purer products. It was assumed t h a t t h e method t h a t would give the highest results when using a temperature not above 110' C. was t h e most nearly correct. All our drying was done in a n aluminium dish, 50 mm. in diameter b y 30 mm. high, provided with a closely fitting cover. The investigations covered the following points:
T H E J O U R N A L O F 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 N I S T R Y Vol.
980
1-The result where the ratio of sand or other dividing material to molasses was kept constant, while the dividing material was varied in size. 2-The results with varying quantities of molasses and constant quantities of dividing material, and with constant quantities of molasses and varying quantities of dividing material. g-The efficiency of various kinds of dividing material. 4-The effect of different temperatures of drying. 5-The effect of a short preliminary drying at a lower temperature, followed by a second mixing and a complete drying. 6-The uniformity of results obtained by drying in an ordinary bath at 105’ C. as compared with drying in a vacuum oven a t lower temperatures. 7-The amount of water or other liquid to add to the substance to give a homogeneous mixture. 8-The time required to mix the samples. 9-The meaning of the term “iron-free sand” as used in the German official methods. Was found t h a t t h e fineness of t h e material had a marked influence on t h e moisture driven off. T h e sand used i n this series of tests, as in all t h e rest of t h e work where sand was t h e dividing material, was a white sea sand t h a t had been digested with hydrochloric acid, washed, and ignited. T h e first series of tests was with sand of four different sizes which were graded b y passing through screens with circular perforations, viz., coarser t h a n I mm., between I mm. and 0.5 mm., between 0 . 5 mm. and 0 . 2 5 mm., and finer t h a n 0 . 2 5 mm. T h e drying was done in a n ordinary glycerol-filled, double-walled oven a t I O j O C. T h e results of t h e investigation of this phase of t h e work are given i n Table I. FIKENESS O F DIVIDING MATERIAL-It
I TABLE Sand No. 1 Coarser than 1 Mm. Time Per of Max, Heating cent Loss Diff. Hrs. 4 5
: i
9 10 12 14 16 18 21 24 30 36 42 48
16.70 16.72 16.87 16.95 17.06 17.10 17.14 17.20 17.28 17.27 17.29 17.32 17.27 17.43 17.35 17.48 17.44
0.18 0.15 0.13 0.01 0.05 0.09 0.06 0.07 0.09 0.18 0.18 0.02 0.1’0 0.08 0.15 0.12 0.12
Sand No. 2 Between 1 and 0.5 Mm. Per cent Max. Loss Diff. 16.98 16.95 17.10 17.12 17.18 17.19 17.25 17.29 17.34 17.34 17.37 17.38 17.35 17.45 17.35 17.51 17.46
0.06 0.10 0.02 0.04 0.04 0.05 0.03 0.06 0.01 0.02 0.07 0.07 0.11 0.02 0.06 0.09 0.10
Sand No. 3 Between 0 5 and 0.25 M m . Per cent Max. Loss Diff. 17.09 17.11 17.17 17.21 17.25 17.26 17.33 17.34 17.44 17.39 17.38 17.38 17.37 17.46 17.44 17.54 17.50
0.25 0.21 0.19 0.11 0.03 0.04 0.05 0.02 0.03 0.10 0.10 0.08 0.01 0.02 0.07 0.03 0.08
Sand No. 4 Less than 0.25 Mm. Per cent Max. Loss Diff. 17.48 17.42 17.50 17.51 17.52 17.58 17.60 17.62 17.69 17.62 17.66 17.69 17.61 17.76 17.77 17.84 17.84
0.19 0.08 0.08 0.07 0.05 0.09 0.10 0.06 0.14 0.08 0.09 0.14 0.14 0.10 0.08 0.06 0.10
Briefly summarized, t h e results show t h a t t h e finest of these sands gave t h e highest moisture content. T h e minimum time of heating any of t h e grades t o obtain marimum results was 8 hrs. T h e loss i n moisture a t t h e end of this time on t h e fine sand was more t h a n on t h e other grades a t t h e end of t h e same period of heating by about 0.2 t o 0.4 per cent, and t h e loss on t h e coarser grade never equaled t h a t on t h e finer, even after 48 hrs. heating. Later on, sand of 40 t o 50 mesh, jo t o 6 0 mesh, 6 0 t o I O O mesh, and finer t h a n I O O mesh was tried out on another sample of molasses with t h e results shown i n Table 11.
12,
No.
IO
TABLEI1 Sand Sand Sand No. 4 No. 5 No. 6 I%?: Time Less than 4 0 t o 50 50 to 6 0 6 0 t o 100 Less than of 0.25 Mm. Mesh Mesh Mesh 100 Mesh Heating Per cent Per cent Per cent Per cent Per cent MATERIAL Hrs. Loss Loss Loss Loss Loss Molasses 4 17.65 17.46 17.58 17.66
?%f$
17.74 7.63 6.17 37.44
8
White Massecuite 8 Raw Massecuite 8 Thick Juice 8
17.60
17.74
... ...
... ... ...
...
17.71
... ... ...
l;:?9
7.62 5.95 37.31
From these results it was concluded t h a t t h e sand must pass a 0 . 2 5 mm. screen t o be suited t o t h e work. T h e still finer grades are as satisfactory and may be used as a mixture containing all sizes from 0 . 2 j mm. down. T h e grade used as a standard had t h e following composition : 50 mesh, 25 per cent 60 mesh, 25 per cent 70 mesh, 22 per cent 100 mesh, 22 per cent Less than 100 mesh, 6 per cent 40 50 60 70
to to to to
R A T I O O F S A N D T O MOLASSES-In both t h e above series, 2; g. of sand and I g. of d r y substance were used. This ratio has been shown t o be t h e one best suited t o moisture determinations. T h e 2 j g. samples gave as high results as t h e 3 0 or 3 5 g. An increase t o 3 0 or 3 5 g. of sand is not objectionable, except t h a t a larger dish t h a n t h e one we used would be needed. I n Table I11 are given t h e results of varying t h e amount of sand used with I g. of d r y substance. Ta\ble IV, on t h e other hand, gives t h e results obtained when t h e amount of dry substance was varied.
TABLE111 Time of Drying Hrs. 4 5 6 7 8
Per Max. cent VariaLoss tion
20 G Sand
Per Max. cent VariaLoss tion
25 G. Sand Per Max. cent VariaLoss tion
3 0 G. Sand Per Max. cent VariaLoss tion
16.98 0 . 0 4 17.440.04 17.38 0 . 0 4 17.45 0.01 17.55 0.01
17.61 0.07 17.610.04 17.64 0.03 17.67 0 . 0 4 1 7 . 6 1 0.09
17.48 0.19 17.420.02 17.50 0.08 17.51 0.07 17.52 0.05
17.23 0 . 1 2 17.750.14 17.62 0.07 17.69 0.10 17.63 0.15
15 G. Sand
TABLEI V 30 G. Sand 35 G. Sand 2 0 G. Sand 35 G. Sand Time Per cent Loss Per cent Loss Per cent Loss of Per cent Loss Heating when when when when Hrs. 1 G. D S. Used 1 G. D. S. Used 1 G. D. S. Used 1 G D. S . Used 4 5 9
4 5 9
17.50 17.61
...
17.61 17.66 17.69
17.47 17.60 17.67
17.63 17.69 17.71
Per cent Loss when
Per cent Loss when
Per cent Loss when
Per cent Loss when
2 G. D. S. Used 2 G. D. S. Used 2 G. D. S. Used 2 G. D . S. Used 17.51 17.49 17.44 17.48 17.55 17.54 17.56 17.50 17.67 17.54 17.61 17.53
Per cent Loss Per cent Loss Per cent Loss Per cent Loss when when when when 3 G. D. S. Used 3 G . D. S . Used 3 G. D. S. Used 3 G. D. S. Used 4 5 9
17.20 17.31 17.46
17.39 17.44 17.53
17.41 17.49 17.58
17.41 17.44 17.52
When N o Water W a s Used in Mixing Per cent Loss Per cent Loss Per cent Loss Per cent Loss when when when when 1 G. D. S Used 1 G. D. S. Used 1 G. D . S. Used 1 G. D. S . Used 4 5 9
17.13 17.33 17.42
17.63 17.63 17.67
I
17.62 17.62 17.69
17.40 17.52 17.60
E F F I C I E N C Y O F D R Y I K G MATERIAL-sea sand, crushed quartz, and pumice stone were t h e only kinds of dividing material investigated. T h e sea sand and crushed quartz gave identical results where t h e conditions of fineness and ratio of d r y substance t o sand were t h e same. T h e pumice s t o n e was more difficult t o manipulate and i n all cases gave lower results i n t h e same length of time of heating.
Oct.,
1920
T H E J O U R N A L OF ILVDUSTRIAL A N D EXGINEERING C H E M I S T R Y
T E M P E R A T U R E EFFECTS-The present work would indicate a temperature of 105’ t o 1 1 0 ’ C. as t h e one best suited t o drying sugar-house products. A temperature below 100’ C. will not give maximum results in any reasonable time. When trying t h e effect of a short preliminary drying at a lower temperature (70’ C., as called for in t h e German methods) i t was found t h a t often, at t h e end of t h e 1 5 min. period of heating, t h e mixture h a d ccset,” so t h a t a second mixing was impossible. The method did not seem t o offer any advantages over t h e direct drying a t 105’ C., and increased t h e time of drying. T h e two following results on molasses are typical, where t h e total time of heating in both methods was 8 hrs. ,SampleA
Our method, per cent moisture., . , , 21.88 German method, per cent moisture 2 1.36
15 Moisture, in vacuum oven (18 h r s ) . . 17 61 Moisture, our method (8 h r s ) . . . . . 17 55
17.78 17.55
Grams of Sand20 17.34 17.61
refer t o sand t h a t does not contain iron as one of i t s constituents, as t h e writer was unable t o find either sand or quartz without at least traces of iron. It is evidently sand free from iron readily soluble i n hydrochloric acid, and a series of tests m a d e with mixtures of sand with metallic iron, ferric oxide, and magnetic oxide of iron indicated t h a t in some cases: t h e oxide of iron in small amounts reduced t h e moisture found. The results were erratic, b u t indicated that. t h e sand used should be free from soluble iron. Sand Sand Alone 79.25
79,25
...
79.02
79.21
78.85
78.67
79.35
79.17
79.27
0.5% 78.98
79.20
------Sand 79.16
+ Fe?Oa-------
0.75% 79.24
0.2570 79.03
Sand
1%
+ FeaOa-----
+ Fe (40 Mesh)---
1.25% 79.05
1.5% 78.98
B
The use of t h e vacuum oven t o determine whether there might be some decomposition of t h e less stable constituents of beet molasses a t t h e higher temperature did not indicate t h a t any decomposition took place, and increased t h e time of drying. It required 18 hrs. t o obtain t h e same results when drying under 1 7 in. of vacuum, a t 80’ t o 83’ C., as were obtained in 8 hrs. when drying a t 1 0 5 ’ C. in an ordinary oven. T h e following tabulation is from one set of tests where I g. of molasses (dry substance) was used with varying amounts of sand.
--
981
25 17.54 17 66
-
30 17.67 17.67
A M O U N T O F LIQUID T O B E ADDED-NO tests were made t o determine t h e maximum amount of water t h a t could be used. It was found t h a t I cc. added t o all of t h e heavier products containing 5 0 per cent or more d r y substance gave a product t h a t on mixing would occupy about 3 t o 4 times t h e volume of t h e original materials. T h e mass i n this condition was very porous and when dry contained many passages through which t h e moisture had escaped. When this amount of water was used there was no tendency for t h e sirup t o leave t h e sand particles when t h e mixture was first heated. If too much water was added, t h e light, porous mixture was n o t obtained. A little experience will teach t h e operator when t h e proper condition is reached. Alcohol was substituted for wates i n a series of tests, b u t it gave no better results and offered no advantages. TIME O F MIxIivG-The proper mixing of a sample requires from 3 t o 5 min., and should be conducted i n two stages. T h e sand, molasses, and water shovld be mixed for 2 t o 3 rnin., then warmed on top of a bath for about 5 rnin., and given a second mixing for I or 2 min. When t h e time of mixing is less t h a n above, there is often found in t h e dried mass small globules of t h e product t h a t are not incorporated with t h e sand. I1 IRON-FREE SAND”-The term “iron-free sand,’’ a s used in t h e German methods: apparently does not
R E S U L T S F R O M N E W METHOD-samples Of sand collected from nine laboratories, and prepared by sizing t o finer t h a n 0 . 2 j mm. and washing and igniting, gave t h e following results. This series of tests was used as a measure of t h e uniformity of t h e dividing material as prepared under varying conditions. Sand XO.
Dry Substance in Molasses
1. . . . . . . . . . . . . . . . . . . . . . . . . . . .
79.06
............................
79.04
..........................
79.03
4
. . . . . . . . . . . . . . . . . . 79.13 . . . . . . . . . . . . . . . . . . 79.06
I
9..
With t h e exception of Sands 3 and 7, all t h e results are very uniform. All results given so far i n this report were run in duplicate or triplicate and it was found very easy t o check within 0.10per cent on a duplicate determination. In nearly all cases, however, two sets of determinations, made on t h e same materials on different days, would not check. A difference of 0 . 2 0 per cent would often occur between duplicates run on different days. It was also found t h a t t h e dried samples were very hydroscopic, and a gain i n weight equivalent t o 0 . 2 0 per cent moisture often occurred when t h e samples stood for I O t o 1 2 hrs. in a desiccator. R E C 0 LIME N D E D M E T H 0 D
I n conclusion, these results are summarized i n t h e following method, which is our standard as used a t t h e present time. Use only sand t h a t will pass a screen with 0.2; mm. perforations; digest t h e sand i n hot hydrochloric acid, wash, and ignite. Use 2 5 t o 30 g. of sand, and dry a n d weigh just previous t o making t h e determination. Weigh into t h e dish not over I g. of d r y substance, add I cc. of water, place t h e dish on t o p of a drying oven until warm, mix for 3 rnin., and warm and mix again, until a perfectly homogeneous mixture is obtained. Dry a t a temperature of 105’ C. for 6 hrs., cool, and weigh. Repeat until t h e loss i n weight after heating for a period of I hr. is less t h a n 0.10per cent. Make all weighings as soon as t h e temperature of t h e desiccator is within 2 ’ C. of t h e temperature of t h e balance. Repeat all determinations where t h e duplicates do not check within 0 . 2 0 per cent.
