44
THE; JOURNAL OF INDUSTRIAL A N D E N G I N E E R I N G C H E X I S T R Y .
the composite sample containing I O per cent. sulphur this method gave 9 . 9 4 per cent. sulphur. Several duplicates made a t the same time gave closely agreeing results. A number of determinations on stock tonics of varying cornposition gave satisfactory results with closely ag-reeing duplicares. The side neck tubes used in the method, shown in the figure are heavy graduated glass tubes 16.4 crn. tall and 3 . 0 cm. in diameter with a side neck carrying a stopcock fused irLabout 5.0 cm. from the bottom of the tube. The use of this side neck was found to be the most satisfactory means of drawing out the aliquot portion. When the tubes are put in the shaking machine they are closed with tight-fitting cork stoppers. No trouble has been experienced by evaporation from this source. Settling the suspended particles in the tube by means of a centrifugal machine was tried, but with only a fair amount of success and i t was found better, when time will permit, to allow the tubes to stand overnight before drawing off the aliquot, thus giving a perfectly clear solution. I t was fo.md most satisfactory to draw off the aliquot into an Erlenmeyer flask of about. 450 cc. capacity. Then during the oxidation with chlorine the flask is closed with a two-hole stopper. One hole is used for the tube from the generator and the other is used for a waste tube to carry offthe excess of chlorine gas. G. M. ?/IACi\jIDER. FEEDAND XICRO-CHEXICAL IABORATORS, S. C. DEPARTMENT OF AGRICULTURE,
Jan.,
The "Asaprol Method" is used by Baier and Keumann, but, owing to the dilution of the serum, is not regarded by some as accurate. Leach,r and Lythgoc and Nurenberg,2 express preferences for the acetic acid method. As it is the method used in the following determinations, i t is described in detail. To 100 cc. of milk add z cc. of z j per cent. acetic acid (sp. gr. 1.035). Heat a t 7 0 ' C. for 2 0 minutes in a beaker covered with a watch glass on the water bath. Then cool for I O minutes in ice water and filter. If the first part of the filtrate is cloudy, it will usually clear up if refiltered through the same filter paper. The serum being obtained in the above manner. the refraction a t 20' C. is determined by the Zeiss immersion refractometer and the specific gravity a t 1 5 " C. by the Westphal balance accurately graduated to four places. As a preliminary, the refraction and fat content of different milk samples from individual cows were determined, the fat being determined by the Babcock method. 'r.IBLE
1.
Milk.
Refraction.
HolsLeiii, pure hred .. Holstein, pure bred .. Holstein, pure bred.. . . . . . . . . . . . . . . . . . . Guernsey, pure bred.. . . . . . . . . . . . . . . . . . Guernsey. pure bred .. Guernsey, pure bred.. . . . . . . . . . . . . . . . . . Guernsey, pure b r e d . . . . . . . . . . . . . . . . . . . Red Poll, pure b r e d . . . . . . . . . . . . . . . . . . . Iicd Poll, pure bred
39.5 39 2 43 . 0 42.5 47.3 44.8 42.7 43.8
I t is oftentimes very difficult for the food chemist to distinguish between honest low-standard milk and fraudulently watered milk. Various methods have been suggested, most of them being more or less unsatisfactory, owing to the time involved and difficulty of analysis, variability of the milk constants, and the consequent unreliability of results. It has been found that the milk serum possesses a fairly constant composition, more so than the milk itself. Different methods have been used for precipitating the casein and obtaining the serum, G. Wiegner and G. Yakuwa, of Goettingen University,I use a dilute solution of CaCl, to obtain the serum. The "Specific Refraction," an arbitrary constant, is then determined. Ackermann2 also uses CaC1, to precipitate the casein and determine the refraction of the serum, claiming that it varies less than serum obtained by any other method. C. Mai and S. Rothenfusser,s also use the CaC1, method, claiming they can detect four per cent. of water. The natural souring method is used by Matthes and Nuller,4 who get very uniform results. 1 "The E x t e n t of Refraction and Specific Gravity of Calcium Chloride Serum of Milk," M i l c i w i ~ t s c h Zenlr., . 5 , 473. 2 "The Refrictometric Detection of A4ddedWater in Xilk," 2. N a h r . Genuss., 1 6 , 586. 3 "The Refraction of Calcium Chloride Xilk Serum," 2. Nahr.Genuss.. 18, 737. 4 "Uber die Untersuchung des Milch Serums mit dem Zeiss'schen Eintansch-Refraktoineter," 2.fiiv afient. Chem., 3, 173.
................... ....................
Angus, pure b r e d . , Xngus. pure b r e d . , .................... Short Horii, pure b r e d . , . , Short I i o r n . pure bred.. .. 1)cvom pure bred, Kerry, ]lure bred.. Grade R e d Poll, pure b r e d . , Averagc. . . . . . . . . . . . . . . . . . . Highest (Guernsey). . . . . . . . . . . . . . . . . . . . Im.:est (IIolstein).
Per cent. f a t . 3.4 3.4 3 0
... 4.7 5.2 3.3 3.7 6.2
...
RALEIGH.
A COMPARISON BETWEEN THE REFRACTION AND THE SPECIFIC GRAVITY OF MILK SERUM FOR THE DETECTION O F ADDED WATER,
1911
45.5 43.2 13.4
.................... .........
43.2
....................
47.3 39.2
5 .o 4.8 4.2 3.5 4.1 4.3 4.6 5.2 4.4 4.3 (Red Poll) 6 . 2 (Holstein) 3.0
This table shows variation in refraction from 39.2 to 4.7.3 and also shows there is no relation between the refraction. and the fat content in the sample used. Table z shows that milk serum from the same cow will vary in refraction if taken a t different times. Hence it would seem impossible to estimate absolutely the amount of added water in a sample even when the original source of the milk is known unless the milk came from a large herd when it might be possible as the composite serum will vary less than the individual serum. 'PADJ,E
Milk
2 First sample.
Guernsey. ......................... Holstein. ......................... fIo!sCeln. .......................... Short Iiorn. ....................... Guernsey. ......................... Red Poll.. ........................ Angus ............................
... ...
...
...
... .
.
I
.
.
I
44.8 39.2 39.8 44.0 47.3 43.8 43.4
'i'rvo uceks later.
43.7 40.8 41 . 2 44.1 42.2 43.9 43.9
Table 3 shows milk systematically adulterated 1
2
Food Inspection and Analysis
"
".\ Comparison of Methods for t h e Preparation of Milk Serutn," T a ~ s
JOURNAL, 1, 38.
NOTES A N D CORRESPONDENCE.
45
and shows ‘the decrease in refraction and specific gravity as water is.added.
attempts to show that he can accurately estimate the amount of water added by taking that figure. Owing to the variability of the specific gravity of TABLE3. various milk serums it would not seem feasible. The Refraction a t 20’ C. Sp. gr. a t 15’ C. Milk “A” pure samples examined by the author vary from 1 . 0 2 7 0 1.0292 0 per cent. H2O.. . . . . . . . 1.0269 5 per cent. Hz0 .............. to 1.0320. 1.0262 RadulescnI and Konigz both state that I O per 1 ,0247 15 per cent. H20 1.0233 20 per cent. H2O cent. of added water decreases the specific gravity Milk “ C ” of the serum 0.0003-0.0010. All other results point 1.0313 1,0285 toward 0.0031 as nearer the exact figure. 5 per cent. HzO . . . . . . . . . . 42.2 1.0280 Most authorities take the lowest limit of refraction 1.0262 15 per cent. HzO.. . . . . . . . . . . . . . . 1.0251 for pure milk serum as 39.0 regarding samples under 1.0234 40.0 as suspicious. This corresponds to the results found by the author. Two Holstein samples were ,0275 0 per cent. H z 0 . . . . . . . . . . . . . . . ,0247 found under 40.0 but it is very unlikely that the com,0237 10 per cent. H2O posite milk of the herd, even of Holsteins, would run ,0224 15 per cent. H2O.. . . . . . under 40.0. Of fourteen systematically adulterated, ,0205 20 per cent. HzO.. ...... ,0195 25 per cent. H2O.. . . . . . . . . . . . . . . . . . . 3 3 . 8 individual samples, j per cent. added water (by volMilk “ E ” ume) was distinguishable in four cases, taking 39.0 ,0250 0 per cent. H2O ....... 4 3 . 0 40.7 .0263 as the limit of pure milk, and the milk would be re5 per cent. HzO.. ....... .. .. 10 Der cent. HIO.. ...... garded as “suspicious” in three more cases. I O per ,0243 15 per cent. H 2 0 . . .................. 3 9 . 3 cent. added water was distinguished in six cases and 1 ,0220 20 per cent. HzO.. . . . . . . . . . . . . . . . . . . 37 .O 1.0209 25 per cent. H20.. .................. 3 5 . 9 was “suspicious” in three cases. 1 j per cent. added Milk “F” water is distinguishable in nine cases and was “sus0 per cent. HzO.. . . . . . . . . . . . . . . . . . . . 41.2 1.0320 picious” in five cases. 2 0 per cent. added water was 5 per cerit. H2O.. ................... 3 9 . 6 1.0259 97 9 1 07qi rn u.n ...... distinguishable in every sample. 1.0219 15 per cent. H2O ........ 1 . 0 2 7 0 is regarded by most authorities as the low 20 per cent. H20.. .................. 3 5 . 9 1.0202 Milk “G” limit for the specific gravity of pure milk serum a t I 5 C. 1.0306 0 per cent. H 2 0 . . ... Leach and Lythgoes present figures showing pure 1.0277 5 per cent. HzO.. ... 1.0251 Holstein milk running as low as 1.0253 but in every 15 per cent. HzO.. ............ 38.7 1.0238 case the milk itself had a specific gravity under the 1.0220 legal standard, 1.0290. The author has been unable 1.0217 25 per cent. HIO.. ........ to find any other authorities presenting authentic The average decrease in refraction due to every figures as low. Milks “ M ” and “ N ” were taken I O per cent. of added water is 2 . 7 . The average from the first milkings of Holstein cows but did not refraction of all the pure samples used is 42.8, the run under the limit, 1 . 0 2 7 0 . Hence, 1 . 0 2 7 0 has been refraction of water 15.0. By a mathematical taken as the low limit for pure milk serum. calculation i t is determined that I O per cent. added The specific gravity of the serums of the 14 indiwater should lower the refraction 2.8, corresponding vidual samples (Table 3, part) was determined on very closely with the results found. the same serum as the refraction, with the result t h a t 5 per cent added water is distinguishable in 8 cases. I O per cent. added water is distinguishable in twelve 38.5 90 per cent. milk.. ......................... cases and I j per cent. of water in fourteen cases. 10 per cent. HzO 90 per cent. milk From the above results i t would appear that the 42.8 - 40.0 = 2.8, decrease due to 10 per cent. water. specific gravity of the serum is a much more delicate The average decrease in specific gravity due to test for added water than the refraction, but owing every I O per cent. added water is 0.0031. The average to the fact that all authorities are not agreed as to specific gravity of all pure samples is 1.0291a t 1 5 C. ~ the low limit of the specific gravity of pure milk The specific gravity of water a t 15’c.is 0.9991. serum, the author would say that it is not as reliable By calculation it is determined that I O per cent. in all cases as the refraction. Both methods comof added water should decrease the specific gravity bined should furnish both a delicate and reliable of the serum 0.0030,corresponding within 0.0001 guide to the detection of added water in milk. As of the results found. both the methods may be used on the same serum, and as the determinations are easily made after the 100 per cent. milk.. ..................... 1.0291 100 per cent. HzO.. ....... .... 0.9991 serum has been obtained, it appears t h a t a com0.92619 90 per cent. milk.. .......... bination of the two methods would insure the certain 10 per cent. H2O.. . ...... 0.09991 I”
&,LA
LL.lC.
. .., .........................
90 per cent. milk, 10 per cent. HzO. , , , 1.0291 1.0261
-
1.’0261 .0.0030
WoodmanT finds that I O per cent. added water lowers the specific gravity of the serum 0.0031 and 1
J . Am. Chem. Soc., 21, 503 (1899).
1 “Mitl ans dem pharm. Ins. und Laboritorium fiir ang chem der Univ. Erlangen (1890)” 3, 93. 2 “Die Untersuchung landswirtschaftlich u n d gewerblich wichtiger Stoffe,” E d . (1898), 36. a “ T h e Detection of Watered Milk,” J . Am. Chem. SOC, 26, I 195
(1904).
46
THg J O U R N A L OF I N D U S T R I A L AND ENGINEERING C H E M I S T R Y .
detection of added water, if in any quantity as would be used in fraudulently adulterated milk. SLEETHR BULL.
Jan., 1 9 1 I
best idea of the scope and thoroughness with which the work has been carried out. ( I ) Geweral Part, by F. W. Hinrichsen. (A) Introduction, ( B ) OccurOHIO STATE UXIVERSITY, rence of Rubber, (C) Properties of the Latex, (D) COLUMBUS,OHIO. Constitution of the Rubber Hydrocarbon, (E) Other Substances Associated with the Rubber Hydrocarbon in Crude Rubber, (F) Physical Properties of Crude BOOK REVIEWS AND NOTICES. Rubber, (G) Chemical Properties of Crude Rubber, (H) Theory of Vulcanization of Rubber, (I) Technical High Speed Steel. The Development, Nature, Treatment, and Use of High Speed Steels, together with some suggestions as Handling of Rubber llaterials, (J) The Properties of to the Problems Involved in Their Use. BY 0. M. BECKER, Vulcanized Rubber. (11) Chemical Analysis of RwbIndustrial Engineer. Cloth, pp, v + 344. McGraw-Hill Book bor, by F. W. Hinrichsen. (A) Analysis of Crude Company, 1910. Price, $4.00 net. Rubber, (B) Analysis of Vulcanized Rubber, (C) Life A very good book from both practical and theo- Tests of Finished Rubber Articles. (111)Mechanretical standpoints. I n a general way the develop- ical Testing of Rubber, by K. Memmler. (A) The ment of high-speed steel and the marvelous advance Practical Carrying Out of Strength Tests on Soft it has caused in machine operation and output are Rubber. (B) Results of Strength Tests on Soft Rubknown, but one begins to understand the real mag- ber according to the Older and More Recent Publicanitude of that advance as he turns the pages of this tions. book. The authors have compiled and arranged very exThe first chapters give a short history of the de- cellently the work of the older and modern investivelopment of metal cutting from earliest times and gators in the field of rubber testing. Of particular methods of manufacture of the ancient steels, includ- interest is the attention given to the physical testing ing the famous Wootz and Damascus brands, the of vulcanized rubber, a division of the subject in most later crucible, open-hearth, Bessemer and electric other works that has been given but slight attention. furnace processes, relate the discovery of MushetNevertheless, from the standpoint of our knowledge the forerunner of the high-speed steels, and the ex- of rubber as a material of construction it is one of tensive experiments of Taylor and White which re- the most important. The discussion of tensile tests, sulted in the wonderful steels which we have to-day. the pressure tests, the machines and apparatus, the Tables are given of the chemical composition of the elongation cur\-es, the hysteresis curves, is very advarious types, and their properties and requirements mirably written. W. @. GIN. for hardening explained according to the latest and accepted theories of metallurgy. The author has Die Chemie der Cellulose. By CARL G. SCFWALBE.First Half. had the aid of such well-known metallurgists as Car8vo. pp. 2 7 2 . Berlin: Gebruder Borntraeger, 1910. penter, Taylor, Stoughton, and others, in ways of This work is unquestionably the best on the chenisuggestion, criticism, use of material, proof-reading, istry of cellulose which has as yet been published. etc. The metallographical explanations and photo- Vhile i t is largely bibliographic in its text, its conmicrographs are good and make clear the theories. struction and method of handling is excellent. This The balance and larger part of the book is devoted first half deals b i t h cotton cellulose as a type, and to the practical part of the subject: the making of considers its behavior and relation towards water, the steel, forging the tools, hardening, tempering, heat, alkalies, acids, salts, dyes, oxidation and reannealing, grinding, etc. The descriptions of the ducing agents, solvents and ferments. The cellulose various types of hardening and annealing furnaces, products produced by hydrolysis and oxidation are pyrometers, machines, etc., are very complete, treated a t some length. The conclusion of the first and apparently no usable type is omitted. Chapters half commences the consideration of the esters of are given on speeds and feeds, new requirements cellulose which, as stated, are to be handled fully in for machines, notes on remodeling old equipment and the second half to be published very soon. the problems involved. The book is well illustrated. H.S. MORK. I n the appendix are given several practical tables. The volume should be of much assistance to the super- Die Unterscheidong der Natiirlichen und Kiinstlichen Seiden. intendent, metallurgist or practical tool man. By DR. ALOIS HERZOG Paper, I z r n o , pp. 78. Dresden: I. M. BREGOWSKY, Theodor Steinkopff, 1910. Price, 7 5 cents, L. W. SPRING. This small pamphlet, containing fifty exccllent Der Kautschuk und seine Priifung. By F. UT.HISRICHSEN and K. microphotographs and illustrations, treats in a full 1 L I m m m R . 8v0, pages x + 263. Leipzig: S. Hirzel, 1910. and complete manner of the methods of differentiaPrice: Paper, 8 marks; cloth, 9 marks ting the various artificial silks from each other and This is, doubtless, the most comprehensive work from the natural product. While both chemical and that has been published up to date on rubber and optical methods are given, the latter receive the greater is particularly valuable in the rubber industry to those attention. Excellent photographs are shown of the interested in the physical testing of vulcanized rub- appearance of the fibers under the ultramicroscope H. S. MORK. ber. A glance Over the table of contents gives the a t a magnification of 2 5 0 0 .
