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Experiments on Determination of Cow Manure in Milk; Moisture Content and Solubility of Cow Manure1
E X P E R I M E N T S ON D E T E R M I N A T I O N OF COW MANURE IN MILK; MOISTURE CONTENT A N D S O L U B I L I T Y OF COW M A N U R E I GEORGE B A R K L E Y TAYLOR
Dairy Division, Market Milk Section, United States Department of Agriculture
A series of experiments was conducted on cow manure from the experimental farm at Beltsville, to determine primarily whether the manure in unstrained milk can be measured quantitatively by chemical methods. A method was found which gave good results provided the original quantity of manure present was fairly large. For average milks, however, this chemical method is impractical on account of the fact that while manure is always present, it is as a rule in such small amounts that it cannot be measured chemically. I t was found that a series of disks containing known amounts of manure could be made which will give fairly accurate results when compared with the sediment from milk after using the sediment tester, by means of a modified method. Since accurate determinations can be made only with unstrained milk, and since all market milk is strained there seems to be no simple practical method of determining the amount of manure present in milk. Along with this work, other experiments were made to determine moisture and solubility in water and milk of fresh and dry manure. Composite samples of manure were collected at different times, covering a period of two months. The cows were fed bran, corn meal, cottonseed meal, and corn silage. The manure, fresh, was a heterogeneous mass, consisting of short straw and fiber, pieces of corn, mixed with a wet dark mass. The samples were weU mixed, but not ground. The moisture was determined by drying the fresh moist sample for five hours in an air oven at 98 to 100"C. The results together t Published by permission of the Secretary of Agriculture.
304
GEORGE B A R K L E Y TAYLOR
with the appro×imate a m o u n t s taken for the determinations are shown below: per teat
Lot, using 5 grams wet material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
84.24 82.32 ~83.89 |83.93
~83. 72
!.83.95 Lot, using about 2 grams wet material . . . . . . . . . . . . . . . . . . . . . . . . . .
[81.85 ~81.48 ]82.U
ts2.0s
Lot, using from 0.5 gram to 6 grams wet material . . . . . . . . . . . . . . .
I82.61 [82.65 ~83.22
|81.04 L82.oo
Lot, using about 1 gram wet material . . . . . . . . . . . . . . . . . . . . . . . . . . .
g3.6,t 82.80 |82.90
I
182.~ Lot, using about 0.5 gram wet material . . . . . . . . . . . . . . . . . . . . . . . . .
82.76 ~82.36
Lot, using about 2 grams wet material . . . . . . . . . . . . . . . . . . . . . . . . . .
f 83.53 ~84.60
Lot, using about 2 grams wet m a t e r i a l . . . . . . . . . . . . .
-. . . . . . . . . . . . .
Lot, using about 2 grams wet mateNal . . . . . . . . . . . . . . . . . . . . . . . . . .
80.63 80.33 84.00
The average of twenty-six determinations was 82.76 per ten| moisture in the fresh manure. This would leave an average of solid m a t t e r in the manure, 17.24 per cent. The moisture content of the air-dried m a n u r e was also made. These determinations were made by drying in an air oven, 98 to 100°C., composite samples of m a n u r e which h a d been allowed to air dry at room temperature.
D E T E R M I N A T I O N OF COW M A N U R E I N M I L K
305
The results were as follows: per ¢~t
Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.79 [5.91 1 5.73
Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(5.43 5.74
15.86
This would leave for the air-dried manure a solid content of 94.26 per cent. S O L U B I L I T Y OF M A N U R E IN W A T E R
The dried manure solids were treated with distilled water; first, by transferring the material to a weighed filter and washing with water to clearness; secondly, by allowing the material to soak in water from one hour to eighteen hours and then filtering through either a weighed filter paper or a weighed cotton disk. The results obtained by these different methods are so nearly alike t h a t the figures are combined to get the averages: Solubility of solid matter in manure after drying to constant weight cALCULATED ON WET ~AKIS
Insoluble
CALCULATED ON DRY BASle
Soluble
Insoluble
Soluble
per cent
per c e n t
p e r cent
14.28 14.20 16.15 14.27 15.73 15.82
1.48 1.56 1.53 1.84 2.16 2.10
~.14 91.38 ~.58 ~.~ ~.22
9.82 8.62 11.41 12.07 11.78
Ave., 15.07
1.78
89.25
10.74
Cent
Summarizing the results thus far obtained we get: For fresh manure (averages) per cant
Moisture ........................................................ 82.76 Solids W a t e r soluble ............................................... I. 78 W a t e r insoluble ............................................. 15.07
306
G E O R G E BAR~rLEY TAYLOR
For air dry manure (averaoe~) per cent
Moisture ........................................................ 5.74 Solids Water soluble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.12 (94.26 × 10.74) Water insoluble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.14 (94.26 X 89.25)
F r o m these results we conclude t h a t with a water solution of fresh manure, 84.54 per cent (82.76 ~- 1.78) will be in solution, leaving 15.07 per cent insoluble; while with an air dried manure, 15.86 per cent (5.74 -t- 10.12) will go into solution, leaving 84.14 per cent insoluble. SOLUBILITY OF MANURE IN MILK
T h e m e t h o d of determining solubility of m a n u r e in milk h a d to be varied from t h a t used in determining solubility of m a n u r e in water on account of the fat a n d other solid m a t t e r in mille which m i g h t remain on the filter. T h e dried material after soaking in mill~ was transferred to a Gooch crucible with a cotton disk, washed with w a r m water followed by ether. Details of this m e t h o d are given further on. T h e dried m a n u r e was lumpy. These lumps were broken up b u t were n o t pulverized. T h e results are as follows: Solubility, in milk, of solid matter i n manure dried at lO0°C., for five hours CS~m~ATEn O~ w ~ r n ~ s m
Ave.
ca~T~n
Insoluble
Soluble
Inaoluble
1 ~ cent
pe r c~nA
l~r ¢e~
ON DnT VaSXS Soluble cen$
16.99 17.26 15.19 (av.-3 15.71 16.41 16.98 15.20
1.16 1.20 0.94(av.-3) 0.65 0.79 0.66 1.27
93.63 93.20 94.22(av.-3) 96.02 95.44 95.34 92.37
6.37 6.80 5.78(av.-3) 3.98 4.56 3.66 7.63
16.25
0.96
94.46
5.54
307
DETERMINATION. OF COW M A N U R E IN" M I L K
Summarizing the results, we obtain the following: For fresh manure (averages) per cent
Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solids Soluble i n m i l k . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Insoluble in milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
82.76 0.96 16.25
For air dried manure (averages) per cen~
Moisture ........................................................
5.74
Solids Soluble in milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Insoluble in milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.22 89.04
From these results we can say that approximately 83.72 per cent of fresh manure is soluble in milk, leaving 16.25 per cent insoluble. On the other hand, with air dried manure, 10.96 per cent will go into solution in milk, leaving 89.04 per cent insoluble. Comparison of the solubility of manure in water and milk shows the following results: SOLUBILITY I N Water
F r e s h m a n u r e (82.76 p e r c e n t w a t e r ) . . . . . . . . . . . . . . . . Air d r i e d m a n u r e (5.74 p e r c e n t water) . . . . . . . . . . . . . .
iii
Milk
c~nt
per cent
84.54 15.86
83.72 10.96
In general, manure in whatever condition is less soluble in milk than in water. Nearly all of the above determinations were made after allowing the foreign material to remain in contact with the milk or in water in bottles over night. Experiments show very little difference in the results by allowing the manure to remain in the milk or water different periods of time. SUSPEN.DED FOREIGN. MATTER I N M I L K
Experiments were made to determine whether manure in bottled milk settled to the bottom of the bottle. Manure, both fresh and air dry, was added to pint bottles of milk and the material allowed to settle over night. A layer about 1 inch from
308
GEORGE BARKLEY TAYLOR
t h e b o t t o m of t h e bottle was siphoned off, the sediment being collected on a Gooch crucible. RESIDUE ON BOTTOM
saUSP~NDRD MAWR
r~nt
p v r cent
88.25
11.75
90.78
Air dried manure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
94.97 89.95
9.28 5.03 10.05
Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
90.99
9.02
f
Wet manure: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
These results v a r y considerably, b u t t h e y prove conclusively t h a t all of t h e sediment in milk is n o t visible--that some of it remains suspended in the liquid. I t m a y be stated t h a t approxim a t e l y 90 per cent of t h e foreign solid m a t t e r in milk settles to t h e b o t t o m of t h e bottle where it m a y be seen. WORK O N CHEMICAL METHODS TO DETERMINE SEDIMENT I N MILK
Experiment 1 a. Pint bottle of milk, containing no sediment, filtered cold, through dried, weighed cotton disk in copper sediment tester; not washed, dried and weighed. Gain in weight (milk residue), 0.0630 gram. b. Repeated w a s h i n g with 50 cc., water, gain in weight ( m i l k r e s i d u e ) , 0.0360 gram. c. Repeated washing with 100 cc. water, gain in weight (milk residue), 0.0320 gram. d. Repeated w a s h i n g with 200 cc. water, gain in weight ( m i l k residue), 0.0370 gram. Experiment 2 a. Pint bottles of clean milk to which were added 0.5 gram, dry extracted manure; mixed, allowed to stand; filtered cold through dried, weighed cotton disk in copper sediment tester, washed with 200 cc. water; dried. Gain in weight over original material (0.5 gram) (milk residue), 0.1460 gram, 0.1180 gram, and 0.1320 gram. b. Repeated, following washing with 200 cc. water and 25 cc. ether. Average increase in weight over original weight, 0.0080 gram. c. Repeated, using only 0.1 gram dry extracted manure, washing
DETERMINATION
OF COW M A N U R E I N M I L K
with 200 cc. water and 25 cc. ether. original weight, 0.0092 gram,
30~
Average loss in weight under
Experiment 3 Different amounts of dry extracted manure were added to pint bottles containing clean milk. This was set aside over night. The material was warmed to about 45°C. (113°F.), filtered through dried and weighed cotton disks in weighed nickel Gooch crucibles, using slight suction. This material was washed with 200 cc. warm water, followed by 25 cc. ether, dried and weighed. D r y manure was used, but this was calculated to wet manure, using moisture factor of 82.8 per cent.
RECOVERED
SAMPLE
Dry
a) ...........
(b) . . . . . . . . . (c) . . . . . . . . . . (d) . . . . . . . . . (e) . . . . . . . . . . (f) . . . . . . . . . . (g) . . . . . . . . . . (h) . . . . . . . . . (i) . . . . . . . . . .
LOSS OR GAIN
Wet
gram8
grams
cram8
grams
0.0860 0.0688 0.0516 0.0344 0.0172 0,0129 0.0086 0.0043 0.0017
0.5000 0.4000 0.3000 0.2000 0.1000 O.0750 0.0500 0.0250 0.0100
0.0810
0.0050 loss 0.0013 loss 0.0036 loss 0.0024 loss 0.0103 gain 0.0041 gain 0.0009 gain 0.0027 gain 0.0053 gain
0.0675 0.0480 0.0320 0.0275 0.0170 0.0095 0.0070 0.0070
Sample (e) is clearly off, and it is left out of the average. The amounts recovered v a r y from 5 mgm. below to 5 mgm. above the amounts used, the average loss and gain almost checking each other. It can be considered, therefore, t h a t the above method is accurate to within 5 mgm. T h e m e t h o d o u t l i n e d a b o v e ( e x p e r i m e n t 3) c a n b e u s e d o n ] y w h e n m i l k c o n t a i n s m o r e t h a n 0.1 g r a m of w e t (fresh) m a n u r e , as t h e e r r o r of 5 m g m . is t o o g r e a t w h e n less m a n u r e is p r e s e n t . I n a c t u a l p r a c t i c e , m a n u r e is s e l d o m f o u n d a b o v e 0.1 g r a m in milk, c o n s e q u e n t l y , t h i s m e t h o d is i n a p p l i c a b l e f o r a v e r a g e a m o u n t s of m a n u r e p r e s e n t in milk. T w e n t y - e i g h t s a m p l e s of u n s t r a i n e d m i l k w e r e e x a m i n e d b y this m e t h o d . Q u a n t i t a t i v e l y , t h e y v a r i e d f r o m 2 t o 20 m g m . P h y s i c a l l y , t h e y s h o w e d n o s u c h v a r i a t i o n , as t h e r e s e e m e d t o
310
GEORGE B A R K L E Y TAYLOR
SHOWING VARYING AMOUNTS OF DIRT IN "UNSTRAINED M~.~.
DETERMINATION
OF COW MANURE
IN
MILK
311
be only a trace of m a n u r e in each disk. Compared with standard disks, there are less t h a n 0.8 m g m . of manure, being onethird to one-twenty-fifth of t h e a m o u n t found quantitatively. A series of twelve cotton disks were prepared, showing quantities of wet m a n u r e from 0.5 gram to 0.005 gram. T h e increase in a m o u n t s was well shown on these disks and t h e y were photographed. I t is t h o u g h t t h a t t h e y will, in a measure, indicate t h e a m o u n t of m a n u r e present in unstrained milk. Clean unstrained milk shows only traces of residue t h a t m i g h t be laid to manure. I t does contain cow hairs a n d white flakes which appear to be epidermis cells from t h e udder. These disks show a m o u n t s of manure, calculated to a wet basis, placed in milk a n d filtered t h r o u g h cotton disks. T h e residues were washed with 200 cc. of warm water followed by 25 cc. ether. T h e following diagram shows t h e rate in percentage of moisture and time of m a n u r e spread o u t to air dry: Time and Moisture
80 70 60 50 4O
30
1
20
10 0
\
\
312
GEORGE B A R K L E Y TAYLOR
Manure present in unstrained milk in quantities greater than 0.1 gram may be fairly accurately determined by filtering through a cotton disk and washing with 200 cc. water, followed by 25 cc. ether. Both the milk and the water should be warmed to about 45°C. before filtering. The disk should be dried and weighed before and after filtration. Manure present in unstrained milk in smaller quantities may be determined by filtering through cotton disks and comparing with standard prepared disks containing known amounts of manure. It must be admitted that the results obtained are only approximate for dairy cow manure. However, considering the heterogeneous composition of this material the averages found are believed to represent the facts fairly well. SUMMARY
The moisture in the cow manure examined averaged nearly 83 per cent. Air dry manure contains about 6 per cent of moisture; 5 per cent of the remaining solid matter is soluble in milk. This would indicate that only 11 per cent of dry manure dissolved in milk, 6 per cent of this being water. Nearly 85 per cent of fresh cows' manure will dissolve in milk, 83 per cent of this being moisture. Manure in whatever condition is less soluble in milk than in water. Of the manure present in bottled milk, 91 per cent will be visible on the bottom of the bottle, leaving 9 per cent of foreign matter in suspension.
Dairy Division, Market Milk Section, United States Department of Agriculture
A series of experiments was conducted on cow manure from the experimental farm at Beltsville, to determine primarily whether the manure in unstrained milk can be measured quantitatively by chemical methods. A method was found which gave good results provided the original quantity of manure present was fairly large. For average milks, however, this chemical method is impractical on account of the fact that while manure is always present, it is as a rule in such small amounts that it cannot be measured chemically. I t was found that a series of disks containing known amounts of manure could be made which will give fairly accurate results when compared with the sediment from milk after using the sediment tester, by means of a modified method. Since accurate determinations can be made only with unstrained milk, and since all market milk is strained there seems to be no simple practical method of determining the amount of manure present in milk. Along with this work, other experiments were made to determine moisture and solubility in water and milk of fresh and dry manure. Composite samples of manure were collected at different times, covering a period of two months. The cows were fed bran, corn meal, cottonseed meal, and corn silage. The manure, fresh, was a heterogeneous mass, consisting of short straw and fiber, pieces of corn, mixed with a wet dark mass. The samples were weU mixed, but not ground. The moisture was determined by drying the fresh moist sample for five hours in an air oven at 98 to 100"C. The results together t Published by permission of the Secretary of Agriculture.
304
GEORGE B A R K L E Y TAYLOR
with the appro×imate a m o u n t s taken for the determinations are shown below: per teat
Lot, using 5 grams wet material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
84.24 82.32 ~83.89 |83.93
~83. 72
!.83.95 Lot, using about 2 grams wet material . . . . . . . . . . . . . . . . . . . . . . . . . .
[81.85 ~81.48 ]82.U
ts2.0s
Lot, using from 0.5 gram to 6 grams wet material . . . . . . . . . . . . . . .
I82.61 [82.65 ~83.22
|81.04 L82.oo
Lot, using about 1 gram wet material . . . . . . . . . . . . . . . . . . . . . . . . . . .
g3.6,t 82.80 |82.90
I
182.~ Lot, using about 0.5 gram wet material . . . . . . . . . . . . . . . . . . . . . . . . .
82.76 ~82.36
Lot, using about 2 grams wet material . . . . . . . . . . . . . . . . . . . . . . . . . .
f 83.53 ~84.60
Lot, using about 2 grams wet m a t e r i a l . . . . . . . . . . . . .
-. . . . . . . . . . . . .
Lot, using about 2 grams wet mateNal . . . . . . . . . . . . . . . . . . . . . . . . . .
80.63 80.33 84.00
The average of twenty-six determinations was 82.76 per ten| moisture in the fresh manure. This would leave an average of solid m a t t e r in the manure, 17.24 per cent. The moisture content of the air-dried m a n u r e was also made. These determinations were made by drying in an air oven, 98 to 100°C., composite samples of m a n u r e which h a d been allowed to air dry at room temperature.
D E T E R M I N A T I O N OF COW M A N U R E I N M I L K
305
The results were as follows: per ¢~t
Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.79 [5.91 1 5.73
Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
(5.43 5.74
15.86
This would leave for the air-dried manure a solid content of 94.26 per cent. S O L U B I L I T Y OF M A N U R E IN W A T E R
The dried manure solids were treated with distilled water; first, by transferring the material to a weighed filter and washing with water to clearness; secondly, by allowing the material to soak in water from one hour to eighteen hours and then filtering through either a weighed filter paper or a weighed cotton disk. The results obtained by these different methods are so nearly alike t h a t the figures are combined to get the averages: Solubility of solid matter in manure after drying to constant weight cALCULATED ON WET ~AKIS
Insoluble
CALCULATED ON DRY BASle
Soluble
Insoluble
Soluble
per cent
per c e n t
p e r cent
14.28 14.20 16.15 14.27 15.73 15.82
1.48 1.56 1.53 1.84 2.16 2.10
~.14 91.38 ~.58 ~.~ ~.22
9.82 8.62 11.41 12.07 11.78
Ave., 15.07
1.78
89.25
10.74
Cent
Summarizing the results thus far obtained we get: For fresh manure (averages) per cant
Moisture ........................................................ 82.76 Solids W a t e r soluble ............................................... I. 78 W a t e r insoluble ............................................. 15.07
306
G E O R G E BAR~rLEY TAYLOR
For air dry manure (averaoe~) per cent
Moisture ........................................................ 5.74 Solids Water soluble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.12 (94.26 × 10.74) Water insoluble . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.14 (94.26 X 89.25)
F r o m these results we conclude t h a t with a water solution of fresh manure, 84.54 per cent (82.76 ~- 1.78) will be in solution, leaving 15.07 per cent insoluble; while with an air dried manure, 15.86 per cent (5.74 -t- 10.12) will go into solution, leaving 84.14 per cent insoluble. SOLUBILITY OF MANURE IN MILK
T h e m e t h o d of determining solubility of m a n u r e in milk h a d to be varied from t h a t used in determining solubility of m a n u r e in water on account of the fat a n d other solid m a t t e r in mille which m i g h t remain on the filter. T h e dried material after soaking in mill~ was transferred to a Gooch crucible with a cotton disk, washed with w a r m water followed by ether. Details of this m e t h o d are given further on. T h e dried m a n u r e was lumpy. These lumps were broken up b u t were n o t pulverized. T h e results are as follows: Solubility, in milk, of solid matter i n manure dried at lO0°C., for five hours CS~m~ATEn O~ w ~ r n ~ s m
Ave.
ca~T~n
Insoluble
Soluble
Inaoluble
1 ~ cent
pe r c~nA
l~r ¢e~
ON DnT VaSXS Soluble cen$
16.99 17.26 15.19 (av.-3 15.71 16.41 16.98 15.20
1.16 1.20 0.94(av.-3) 0.65 0.79 0.66 1.27
93.63 93.20 94.22(av.-3) 96.02 95.44 95.34 92.37
6.37 6.80 5.78(av.-3) 3.98 4.56 3.66 7.63
16.25
0.96
94.46
5.54
307
DETERMINATION. OF COW M A N U R E IN" M I L K
Summarizing the results, we obtain the following: For fresh manure (averages) per cent
Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Solids Soluble i n m i l k . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Insoluble in milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
82.76 0.96 16.25
For air dried manure (averages) per cen~
Moisture ........................................................
5.74
Solids Soluble in milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Insoluble in milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.22 89.04
From these results we can say that approximately 83.72 per cent of fresh manure is soluble in milk, leaving 16.25 per cent insoluble. On the other hand, with air dried manure, 10.96 per cent will go into solution in milk, leaving 89.04 per cent insoluble. Comparison of the solubility of manure in water and milk shows the following results: SOLUBILITY I N Water
F r e s h m a n u r e (82.76 p e r c e n t w a t e r ) . . . . . . . . . . . . . . . . Air d r i e d m a n u r e (5.74 p e r c e n t water) . . . . . . . . . . . . . .
iii
Milk
c~nt
per cent
84.54 15.86
83.72 10.96
In general, manure in whatever condition is less soluble in milk than in water. Nearly all of the above determinations were made after allowing the foreign material to remain in contact with the milk or in water in bottles over night. Experiments show very little difference in the results by allowing the manure to remain in the milk or water different periods of time. SUSPEN.DED FOREIGN. MATTER I N M I L K
Experiments were made to determine whether manure in bottled milk settled to the bottom of the bottle. Manure, both fresh and air dry, was added to pint bottles of milk and the material allowed to settle over night. A layer about 1 inch from
308
GEORGE BARKLEY TAYLOR
t h e b o t t o m of t h e bottle was siphoned off, the sediment being collected on a Gooch crucible. RESIDUE ON BOTTOM
saUSP~NDRD MAWR
r~nt
p v r cent
88.25
11.75
90.78
Air dried manure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
94.97 89.95
9.28 5.03 10.05
Average . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
90.99
9.02
f
Wet manure: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
These results v a r y considerably, b u t t h e y prove conclusively t h a t all of t h e sediment in milk is n o t visible--that some of it remains suspended in the liquid. I t m a y be stated t h a t approxim a t e l y 90 per cent of t h e foreign solid m a t t e r in milk settles to t h e b o t t o m of t h e bottle where it m a y be seen. WORK O N CHEMICAL METHODS TO DETERMINE SEDIMENT I N MILK
Experiment 1 a. Pint bottle of milk, containing no sediment, filtered cold, through dried, weighed cotton disk in copper sediment tester; not washed, dried and weighed. Gain in weight (milk residue), 0.0630 gram. b. Repeated w a s h i n g with 50 cc., water, gain in weight ( m i l k r e s i d u e ) , 0.0360 gram. c. Repeated washing with 100 cc. water, gain in weight (milk residue), 0.0320 gram. d. Repeated w a s h i n g with 200 cc. water, gain in weight ( m i l k residue), 0.0370 gram. Experiment 2 a. Pint bottles of clean milk to which were added 0.5 gram, dry extracted manure; mixed, allowed to stand; filtered cold through dried, weighed cotton disk in copper sediment tester, washed with 200 cc. water; dried. Gain in weight over original material (0.5 gram) (milk residue), 0.1460 gram, 0.1180 gram, and 0.1320 gram. b. Repeated, following washing with 200 cc. water and 25 cc. ether. Average increase in weight over original weight, 0.0080 gram. c. Repeated, using only 0.1 gram dry extracted manure, washing
DETERMINATION
OF COW M A N U R E I N M I L K
with 200 cc. water and 25 cc. ether. original weight, 0.0092 gram,
30~
Average loss in weight under
Experiment 3 Different amounts of dry extracted manure were added to pint bottles containing clean milk. This was set aside over night. The material was warmed to about 45°C. (113°F.), filtered through dried and weighed cotton disks in weighed nickel Gooch crucibles, using slight suction. This material was washed with 200 cc. warm water, followed by 25 cc. ether, dried and weighed. D r y manure was used, but this was calculated to wet manure, using moisture factor of 82.8 per cent.
RECOVERED
SAMPLE
Dry
a) ...........
(b) . . . . . . . . . (c) . . . . . . . . . . (d) . . . . . . . . . (e) . . . . . . . . . . (f) . . . . . . . . . . (g) . . . . . . . . . . (h) . . . . . . . . . (i) . . . . . . . . . .
LOSS OR GAIN
Wet
gram8
grams
cram8
grams
0.0860 0.0688 0.0516 0.0344 0.0172 0,0129 0.0086 0.0043 0.0017
0.5000 0.4000 0.3000 0.2000 0.1000 O.0750 0.0500 0.0250 0.0100
0.0810
0.0050 loss 0.0013 loss 0.0036 loss 0.0024 loss 0.0103 gain 0.0041 gain 0.0009 gain 0.0027 gain 0.0053 gain
0.0675 0.0480 0.0320 0.0275 0.0170 0.0095 0.0070 0.0070
Sample (e) is clearly off, and it is left out of the average. The amounts recovered v a r y from 5 mgm. below to 5 mgm. above the amounts used, the average loss and gain almost checking each other. It can be considered, therefore, t h a t the above method is accurate to within 5 mgm. T h e m e t h o d o u t l i n e d a b o v e ( e x p e r i m e n t 3) c a n b e u s e d o n ] y w h e n m i l k c o n t a i n s m o r e t h a n 0.1 g r a m of w e t (fresh) m a n u r e , as t h e e r r o r of 5 m g m . is t o o g r e a t w h e n less m a n u r e is p r e s e n t . I n a c t u a l p r a c t i c e , m a n u r e is s e l d o m f o u n d a b o v e 0.1 g r a m in milk, c o n s e q u e n t l y , t h i s m e t h o d is i n a p p l i c a b l e f o r a v e r a g e a m o u n t s of m a n u r e p r e s e n t in milk. T w e n t y - e i g h t s a m p l e s of u n s t r a i n e d m i l k w e r e e x a m i n e d b y this m e t h o d . Q u a n t i t a t i v e l y , t h e y v a r i e d f r o m 2 t o 20 m g m . P h y s i c a l l y , t h e y s h o w e d n o s u c h v a r i a t i o n , as t h e r e s e e m e d t o
310
GEORGE B A R K L E Y TAYLOR
SHOWING VARYING AMOUNTS OF DIRT IN "UNSTRAINED M~.~.
DETERMINATION
OF COW MANURE
IN
MILK
311
be only a trace of m a n u r e in each disk. Compared with standard disks, there are less t h a n 0.8 m g m . of manure, being onethird to one-twenty-fifth of t h e a m o u n t found quantitatively. A series of twelve cotton disks were prepared, showing quantities of wet m a n u r e from 0.5 gram to 0.005 gram. T h e increase in a m o u n t s was well shown on these disks and t h e y were photographed. I t is t h o u g h t t h a t t h e y will, in a measure, indicate t h e a m o u n t of m a n u r e present in unstrained milk. Clean unstrained milk shows only traces of residue t h a t m i g h t be laid to manure. I t does contain cow hairs a n d white flakes which appear to be epidermis cells from t h e udder. These disks show a m o u n t s of manure, calculated to a wet basis, placed in milk a n d filtered t h r o u g h cotton disks. T h e residues were washed with 200 cc. of warm water followed by 25 cc. ether. T h e following diagram shows t h e rate in percentage of moisture and time of m a n u r e spread o u t to air dry: Time and Moisture
80 70 60 50 4O
30
1
20
10 0
\
\
312
GEORGE B A R K L E Y TAYLOR
Manure present in unstrained milk in quantities greater than 0.1 gram may be fairly accurately determined by filtering through a cotton disk and washing with 200 cc. water, followed by 25 cc. ether. Both the milk and the water should be warmed to about 45°C. before filtering. The disk should be dried and weighed before and after filtration. Manure present in unstrained milk in smaller quantities may be determined by filtering through cotton disks and comparing with standard prepared disks containing known amounts of manure. It must be admitted that the results obtained are only approximate for dairy cow manure. However, considering the heterogeneous composition of this material the averages found are believed to represent the facts fairly well. SUMMARY
The moisture in the cow manure examined averaged nearly 83 per cent. Air dry manure contains about 6 per cent of moisture; 5 per cent of the remaining solid matter is soluble in milk. This would indicate that only 11 per cent of dry manure dissolved in milk, 6 per cent of this being water. Nearly 85 per cent of fresh cows' manure will dissolve in milk, 83 per cent of this being moisture. Manure in whatever condition is less soluble in milk than in water. Of the manure present in bottled milk, 91 per cent will be visible on the bottom of the bottle, leaving 9 per cent of foreign matter in suspension.