544
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 .
No. 5 . made from whole milk modified with whey. When dissolved with the proper proportion of water it has approximately the composition of human milk. No. 6, made from light cream and No. 7 from heavier cream. Nos. 1-7, made from known milks. No. 8 , evidently from whole milk with the addition of cane sugar. No. 9 and No. 10, evidently from skimmed milk with the addition of small amounts of cane sugar. Nos. 8-10 made from unknown milks. MERRELL-SOULE Co., LABORATORY, N. Y..Feb. 17, 1912. SYRACUSE.
A MODIFICATION OF THE BABCOCK TEST AS APPLIED TO THE ESTIMATION O F FAT I N DESICCATED MILK. By N. GREGORY REDMOND. As the Babcock method is the one most generally used by dairymen and manufacturers using milk products, either it or some equally unsuitable method is often applied t o determine t h e fat in desiccated milk. Van Slyke’ appreciates the fact t h a t the ordinary Babcock method, when used with milk powder, gives results which are too low. It occurred t o the writer t h a t it would be a n advantage if the Babcock test could be so modified t h a t it would give accurate results. This modification was finally worked out, and has been successfully used for several months. To test the accuracy of the method, the fat was determined on a sample of desiccated milk by several different methods. One of those used was the Werner-Schmidt method. That this method is trustworthy has been shown by H. D. Richmond2 and also by a n abstract in The Analyst of a recent paper by A. BurrS on the “Composition of Dried Milk Powder.” The results which are shown in the table prove t h a t the direct extraction of t h e milk powder with anhydrous ether gives results which are too low. I n each case where a direct extraction was made, the powder was first dried a t g o o C. t o IOOO C. for a t least five hours. I n using the Werner-Schmidt method the fat was redissolved in petroleum ether and a n allowance made for any impurities. This was also done with the direct extractions when the fat appeared to be impure. I n the ordinary Babcock test, the powder was weighed and transferred t o the test bottle, then dissolved in warm water, cooled, and concentrated sulphuric acid added. This prevents any error whi h might occur from inaccurate sampling by measuring a n aliquot part of a IO per cent. or 20 per cent. solution. The general experience of this laboratory has been t h a t this method is about 3 per cent. low. The accuracy of the new method is shown by the fact t h a t the average of ten determinations by the various methods (excluding the direct extraction with ether distilled over sodium and the ordinary Babcock method) is 28.49 per cent. fat, and the average of four determinations by the new method is 2 8 . 6 2 per cent. fat. A determination in duplicate by the new method can easily be made in less than one hour. Some of its advantages are cheapness, simplicity, speed and accuracy. The following is a description of the method: Weigh 2.5 grams of milk powder and transfer i t to an ordinary Babcock milk bottle, graduated to IO per cent. A glass funnel (about 2” in diameter and with the stem cut off t o %”) is inserted in the neck of the bottle and is of great help in transferring the powder. Add 31 cc. of dilute sulphuric acid (395 cc. concentrated H2S04diluted to I liter) and place the bottle upright in a dish of gently boiling water. Shake frequently and keep in the boiling water until all the powder is dissolved and the solution is dark brown in color. This usually takes from 7 t o IO minutes. After removing the bottle from the
’ “Modern Methods of Testing Milk and Milk Products.” 1906, Ed., p.
86.
a The Analyst. Si, No. 364. pp. 218-224. a Ibid., 86. No. 423, p. 279.
July,
1912
water add 12 cc. concentrated H2S04 (sp. gr. I .82-I .83) and mix thoroughly, taking care to keep the solution out of the neck of the bottle. Agitate with a rotary motion. Place the bottle in a centrifuge and whirl for 4 or 5 minutes. Add hot water until the solution reaches the lower end of the neck, whirl again for I minute, then.add hot water until the fat rises. Whirl again for I minute. I n order to secure accurate results, the fat column must be read a t a temperature not above 140’ F. nor below 130’ F; by setting the bottle in water, the desired temperature may be reached. Readings should be made t o o .05 on the bottle. The reading multiplied by 7 . 2 gives the percentage of fat. ’ 2.5 grams : 18 grams = Reading : X. If reading = 4.00, then 2.5 : 18 = 4.00 : X. I8 O r X = 4.00 X - = 4.00 X 7 . 2 or X = 28.80 per cent. 2.5
A COMPARISONOF DIFFERENTMETHODS
OF
DETERMINING FATIN MILK
POWDER. Fat. Per cent. Squibb’s ether-16
hours’ direct extraction. . . . . . 2 8 . 3 0
Ether containing 5 cc. HzO per liter, 16 hours’ direct extraction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ether containing 5 cc. H20 per liter, 18 hours’ direct extraction.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ether containing 5 cc. H20 per liter, WernerSchmidt method.. ........................... Anhydrous ether (distilled over sodium), WernerSchmidt method.. ........................... Average of ten determinations above. . . . . . . . . . . . By the proposed new method. ...................
Anhydrous ether (distilled over sodium). 16 hours’ direct extraction. Babcock method.. .............................
............................
1
28.45 28.50 2 8 . 5 5 t! 28.50 28.60 28.50 28.56 28.39 1 28,54J
I 1
Averages. 28.37 28.52 28.55 28.53 28.46 28.49
1
28.801 28.44 28.44 I 28.80) 13.55 13.40 25.20 25.201
1
2 8 , 62
13 , 4 7
25.20
Babcock bottles vary in volume. It is more convenient to use bottles which hold at least 45 cc. of water when filled to the lower end of the neck. The bottle should be thoroughly cleaned, rinsed with alcohol and dried (to prevent powder sticking in the neck) before using. This insures clear and accurate readings. Commercial sulphuric acid has been used in making the dilute H,SO, solution and good results were obtained. It is better, however, t o use c. p. acid and thus avoid contamination of the fat column by impurities in the acid. LABORATORY, MERRELL-SOULECo., SYRACUSE, N. Y.,Feb. 17, 1912.
ALUNDUM NOT CONSTANT I N WEIGHT. B Y E. B. FORBES. The invention of porous earthenware laboratory utensils immediately satisfied a large number of urgent and long-standing requirements. As is inevitable under such circumstances this new ware has been put to some uses which it is not adapted to serve, and a correct appreciation of its very great value in the laboratory requires that we search out and recognize its limitations. I n a n effort to shorten and improve upon the usual method for crude fiber determination, we followed the Morgan P. Sweeney mpdification except that instead of straining through an unstandardized cloth we conducted our filtration, washing and ignition all without transfer, in an alundum extraction capsule. It appeared to be a beautiful method, and through the substitution of a n efficient, standardized filter for the rag strainer it seemed to remove from this very unscientific determination one of the principal grounds for our objections; but things were not as they seemed. Alundum is not constant in weight through treatment with water and heat.
