F e b . , 1914
T H E J O C R S A L 0 F I S D L-S T RI-4 L A S D E S G I S E E RI S G C €1E M I S T K F
It is seen t h a t t e n of t h e twenty-five preservatives tested fall belov I per cent, or more accurately 0 . 6 j per cent, for their killing point for Pomes aizmsrrs; P o m e s piiricola was used with only fourteen of t h e m b u t of these ten fell below I per cent! or more accurately, o.;j per cent. I t is interest.ing t o note t h a t sodium fluoride a n d Fraction I 1 of coal t a r creosote head t h e list with nearly equal ?oxicities. Just what constituents of t h e naphthalene fraction are t h e effective ones is not known a t present, b u t t h e work of other investigators indicates t h a t pure naphthalene has low toxic properties. T h e very favorable results froin sodium fluoride would place this in t h e first r a n k of mater-soluble preservatives. This. together n-ith several other fluorine compounds, has come into considerable use abroad, particularly in Austria, a n d i t is t h e opinion of t h e writers t h a t we have i n these substances very efficient wood preservatives which c a n be a d a p t e d t o use in m a n y situations. T h e i n d u s t r y particularly needs some substance which c a n safely be recommended for building timbers. I n comparing t h e two carbolineums with coal t a r creosote i t is seen t h a t approximately 3 0 per cent of t h e former distils below 3 2 0 ' C., while 74 per cent of t h e creosote comes over. This indicates t h e greater toxicity of t h e lower boiling constituents. Xs t o what causes t h e greater toxicity of S. P. F. Carbolineum over -4venarius Carbolineum we are n o t prepared t o s a y , b u t t h e fact t h a t t h e former is higher in t a r acids is very suggestive. T h e poor sholring made by copperized oil against both fungi in di c a t e s t h a t ad ding co p p er i n t his form t o 1o w -t o xi c petroleum or vegetable oils is of very doubtful value. I n conclusion, t h e writers are prone t o t a k e a T-ery conservative position when i t comes t o analysis of t h e d a t a presented a n d generalizations d r a v n therefrom. TVe wish t o strongly emphasize again t h e fact t h a t toxicity alone does not necessarily gi\-e a direct comparison of t h e service value of preservatives, a n d t h a t all t h e s t a t e m e n t s made comparing different. substances refer t o t h e toxic properties only. However, we do feel t h a t t h e results here set forth n-ill prove of considerable ].due in outlining further tests n-hich r i l l serve t o bring out actual sen-ice values. \Ye wish t o record our acknon-ledgments t o Dr. H a r m Iletcalf. Pathologist in Charge, Laboratory of Forest Pathology, Bureau of Plant I n d u s t r y , TTashington. D. C . ; t o l l r . Howard F. Tl'eiss, Director of the Forest Products Laboratory, C . S. Forest Service, N a d i s o n , TTisconsin. for facilities a n d material placed at our disposal; also t o l l r . Ernest Bateman, Chemist in Forest Products, Forest Products Laboratory, mho has supplied all t h e d a t a on t h e physical a n d chemic a1 prop e r t i e s of t h e preservatives e x a mi ne d . LABORATORY OF FOREST B L R E A UOF
PAIIIOLOGY
PI.AS1 ISDUSTRY
h I A D I S O X , xvISCOSSIS
A RAPID METHOD FOR DETERMINING THE PERCENTAGE O F CASEIN IN MILK B y '&'. 0 ,
\t''aLKER
Received February 14, 1913
During t h e past fern years dairymen have been
131
giving a good deal of attention t o t h e advisability o f taking into account t h e percentage of castyin n-hen paying patrons for milk t o be used in cheese-making. Some a d r o c a t e paying on a f a t basis only, others on t h e f a t a n d casein basis. It is not t h e object of this article t o discuss t h e merits of either of these methods, b u t t o outline a process which has been tried out i n t h e author's laboratory ' f o r quickly a n d simply a r riving at t h e a m o u n t of casein in milk. I t is well k n o n n t h a t several methods have been suggested of late, t h e most promising probably being t h e centrifugal method of H a r t . This has, apparently, yielded satisfactory results in m a n y cases, b u t has been found t o give varying results with preserved samples, a n d with fresh milk, under different conditions of temperature, etc. Research into t h e constitution of t h e protein molecule has revealed t h e probability of i t s consisting of a complex linkage of a large n u m b e r of amino acids. T o illustrate this linking u p of amino acids we may use t h e following equation, which shows how one molecule of a simple amino acid, such as amino-propionic acid, m a y become bound t o a molecule of another amino acid such as amino-acetic acid: H H H 0 , I \C--d-H / I H-C--C--C //O H-0 , '0-H H-- hT- H I HH-KN-H
+
H
H
H
0 =
H-C--C-C,
'C-C-H
+HOH
Both t h e molecules of amino-propionic acid a n d amino-acetic acid, as indicated above, possess a n alkaline (amino) group,
H-1-H,
as well as a n acidic
0 group. -C/ , a n d when t h e y combine we m a y 'OH have t h e union taking place in t h e manner indicated, in which t h e alkaline (amino) group of one molecule interacts with t h e acidic group of t h e other molecule, t h u s leaving a n alkaline group a n d a n acidic group still existing in t h e product, which m a y be looked upon, for our purpose, as a r e r y simple representative of the proteins. It has further been observed t h a t when formaldehyde is added t o proteins, the neutral character of t h e molecule disappears, with t h e result t h a t t h e acidic property predominates strongly. I t is thought t h a t t h e formaldehyde reacts with t h e alkaline groups forming methylene derivatives, t h u s l e a r i n g t h e acidic groups free t o act. These acidic groups m a y now be neutralized with s t a n d a r d alkali, a n d if t h e value of t h e alkali in t e r m s of protein be known, t h e percentage of protein present m a y be estimated.
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
I3 2
Hugo Schiff’ was t h e first t o point out t h e importance of t h e reaction between formaldehyde a n d amino acids. S. P. L. Sorensen worked out most of t h e details for t h e quantitative application of t h e reaction for estimating amino acids. H. Droop Richmond adapted t h e reaction t o t h e estimation of total proteins in milk. T h e a u t h o r decided t o apbly t h e reaction to t h e estimation of casein in milk, with t h e use of t h e alkali commonly used for t h e ‘acid test’ now in general use in cheese factories in Ontario. In hoping t o apply t h e reaction t o estimate casein only, t h e problem is, of course, t o obtain t h e proper factor, which, when multiplied by t h e q u a n t i t y of alkali necessary t o neutralize t h e acidity developed after t r e a t m e n t with formaldehyde, will give t h e q u a n t i t y of casein in t h e sample. Since t h e formaldehyde reacts with both casein a n d albumin, and, since t h e amounts of these two in milk do not bear a cons t a n t ratio t o one another, it was not t o be expected t h a t a factor holding good in all cases could be obtained. However, a factor has been obtained t h a t is giving unexpectedly good results. T h e alkali solution was ninth normal sodium hydroxide, a n d t h e formaldehyde was t h e commercial article (40 per cent) made neutral t o phenolphthalein. T h e method for arriving a t t h e factor was t h e following: I O cc. of milk were transferred b y means of a pipette t o a porcelain casserole. A fairly large quant i t y of phenolphth’hlein solution (about 1 cc. of a I per cent solution) was added next. The alkali was then r u n in with constant stirring with a glass rod until a fairly deep pink color developed. So far t h e test is exactly t h e same a s t h e ordinary “acid test.” N o account was kept of t h e alkali used t o bring t h e sample of milk t o t h e neutral point. About 2 cc. of t h e neutral formaldehyde solution were next added, with t h e result t h a t t h e pink color a t once disappeared. T h e reading of t h e b u r e t t e was t h e n taken, a n d alkali again added with stirring until t h e same degree of color developed. T h e reading of t h e burette was again taken, t h e difference between t h e two readings being t h e amount of alkali used in t h e second titration. Sample 1..
Kjeldahl method
....
2.................... 3. . . . . . . . . . . . . . . . . . . . . 4.................... 5 ..................... 6.....................
i..................... 8 . .. . . . . . . . . . . . . . . . . . 9..................... 10 . . . . . . . . . . . . . . . . . . . . . 11. . . . . . . . . . . . . . . . . . . . .
1 2 . .. . . . . . . . . ... 13 . . . . . . . . . . . . . . . . . . . .
2.45 2.45 2.61 2.51 2.77 2.53 2.32 2.96 2.69 2.45 2.32 2.52 2.31
New method
.
2.53 2.45 2.63 2.52 2.69 2.61 2.36 2.96 2.66 2.36 2.30 2.56 2.27
DiRerence
+ O . 08 0.00 +0.02 fO.01
.
-0.08 4-0.08 t0.04 0.00 -0,03 -0.09 -0.02 f0.04 -0.04
Another I O cc. of milk was next treated by t h e official Kjeldahl method for casein, a n d from this result t h e value of I cc. of N / g alkali in terms of casein was determined. F r o m a large number of samples t h e value: I cc. N / g alkali = 1.63 per cent casein was arrived a t . Above is a comparison of some results obtained b y t h e official Kjeldahl method a n d t h e new method, using’ t h e factor 1.63. 1
Annulen, 310, 25 (1900); 319, 59 (1901); 325, 348 (1902).
Yol. 6, NO. 2
I n determining t h e percentage of casein in a given sample of ‘milk t h e procedure is exactly as outlined for determining t h e factor, omitting t h e Kjeldahl determination. The test occupies only a few moments. I t has, of course, t h e disadvantage t h a t only one sample can be handled a t a time, b u t as a number of samples can be run in a few minutes, this may not prove t o be of very great consequence. From t h e fact t h a t t h e chemicals a n d apparatus required are exactly t h e same as are in common use in cheese factories, with t h e exception of t h e formaldehyde which is very inexpensive, it is thought t h a t t h e method should commend itself t o t h e serious consideration of dairymen. It is, of course, important t h a t t h e formaldehyde solution be kept neutral. This may be accomplished by adding a few drops of t h e indicator solution (phenolphthalein) t o t h e formaldehyde in t h e bottle, a n d then adding t h e alkali until a pink color develops. This fades in t h e course of time, a n d t h e formaldehyde must t h e n be treated again with t h e alkali. The proper amounts of indicator (I per cent solution) a n d formaldehyde solutions t o be used have been found t o be about I cc. of t h e former a n d 2 cc. of the latter. An excess of either, however, occasions no error. I n t h e manipulation of t h e test it is well t o add sufficient of t h e alkali during t h e first titration t o bring t h e color t o a decidedly deep pink, a n d a t t h e second titration t o bring t h e color t o t h e same shade. T h e titrations are best carried out in a white cup or porcelain casserole. If it is desired t o estimate t h e acidity also, the reading of t h e burette may be taken after t h e first titration. T h e casein is t h e n estimated from the difference between t h e first a n d second titrations. T h u s both t h e acidity a n d t h e casein are estimated in the one operation. Those dairymen who use a n d g cc. of mi1,k as t h e sample will, of course, employ t h e same factor. The test is a t present recommended for unpreserved milk only, although t h e author expects t o be able t o announce a suitable preservative a t a n early date. T h e following table is given for t h e use of those not wishing t o take t h e time t o multiply t h e amount of alkali used by t h e factor 1.63. Per c e n t casein
C c . S / 9 alkali used
.
1 . 0 0. . . . . . . . . . . . . . . . . . . . . . . . . . 1 . 0 5. . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . 1 0. . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . 1 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . 2 0. . . . . . . . . . . . . . . .
1. 6 3 1.71 1.79 1.87
1 . 2 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . 3 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.04
..................... .....................
2.12 2.20 2.28
1.45 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.36 1 . 5 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.44 1 . 55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.53 1 . 6 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.61 1 . 6 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 . 6 9 1 . 7 0. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.ii 1 . i 5. . . . . . . . . . . . . . . . . . . . . . . . . . . 2.85 1 . 8 0. . . . . . . . . . . . . . . . . . . . . . . . 1 . 9 0. . . . . . . . . . . . 1 . 9 5. . . . . . . . . . . .
............
............
2.00 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Instead of using a
IO
3.10 3.18 3.26
cc. pipette for taking t h e
Feb., 1914
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
samples a n d consequently having t o multiply t h e a m o u n t of alkali used b y 1.63, i t is advisable t o use a 16.3 cc. pipette, i n which case, t h e reading on t h e burette denotes directly t h e percentage of casein. A very convenient a n d simple form of acidimeter has been lately p u t on t h e market b y t h e a u t h o r which m a y be used for both t h e “acid test” a n d t h e “casein test.” A series of comparative tests, using both t h e new method a n d t h e centrifugal method, has been carried on at t h e Eastern Dairy School, Kingston. T h e tests were made independently on t h e same milks b y Messrs. Echlin a n d Cameron. N r . Echlin did t h e work with t h e new test, a n d 11r. Cameron t h a t with t h e centrifugal method. T h e resulting figures, as can be seen from t h e following table, are in surprisingly close agreement. Centrifugal method 2.6 2.7 2.5 2.55 2.55 2 i5 2.3 2.3 2.6 2.5 2.5 2.25 2.25 2.2 2.5 2.6 2.7 2.3 2.3 2.5 2.45 2.56 2.56 2.55 2.55 2.55
New method 2.64 2.69 2.44 2.61 2.61 3.61 2.36 2.36 2.61 2.53 2.53 2.28 2.28 2.20 2.56 2.63 2.67 2.43 2.43 2.43 2.35 2.67 2.67 2.59 2.59 2.59
Centrifugal method 2.25 2.3 2.35 2.6 2.5 2.5 2.25 2.25 2.2 2.35 2.35 2.35 2 4 2.4 2.35 2 35 2.35 2.3 2.3 2.4 2.4 2.4 ’
j 3 2.25.
New method 2.35 2.35 2.43 2 59 2.51 2.51 2.27 2.27 2.19 2.35 2.35 2.35 2.43 2.43 2.35 2.35 2.35 2.27 2.27 2.43 2.43 2.43 2.27 2.27
Centrifugal method 2.2 2.4 2.4 2.4 2.5 2.45 2.4 2.4 2.45 2.5 2.3 2 35 2.4
Thr average difference for the above sixty-three 0.03+. GORDOKHALL OF CHEMISTRY SCHOOL OF MINING,KINGSTOX. ONTARIO
.. .. ..
..
..
..
.. .. .. .. .. ..
New method 2.27 2.43 2.43 2 43 2.59 2.51 2.43 2.43 2.49 2.55 2.27 2.35 2.43
..
..
..
.. .. .. .. *.
.. ..
.. .. ..
determinations is
I. A NEW ELECTRICALLY CONTROLLED AND TIMED ASPHALT PENETROMETER 11. THE EFFECT ON PENETRATIONS OF VARIATIONS IN STANDARD NEEDLES B y HBRMAXNW. MAHR
Received July 14, 1913
I Success in t h e laying of asphalt pavements is probably more dependent on t h e proper consistency of t h e asphalt cement used t o bind t h e mineral aggregate t h a n on a n y other feature. T h e varied origins of modern bituminous cements have made t h e determination of their consistency t h e most i m p o r t a n t test applied t o these materials. Formerly a few varieties of s t a n d a r d solid biteurnens, quite uniform in character, fluxed with definite proportions o€ petroleum residuums of s t a n d a r d a n d specified composition, yielding cements of a desired consistency, formed t h e bulk of t h e asphaltic cements; b u t recently m a n y paving bitumens obtained b y distilling asphaltic
I33
petroleums t o t h e consistency of cements have come on t h e market. Proximate chemical analysis is of little value in fixing. their origin, a n d t h e highway chemist is obliged t o rely almost solely on determinations of consistency t o ascertain their suitability. There are several rough methods for determining t h e consistency of asphaltic cements, b u t t h e most generally used scientific determination is b y means of penetrometers. T h e first of these instruments was devised b y Bowen, a n d has been followed b y machines working on t h e same principle by Kenyon, Dow a n d t h e New York Testing Laboratory. T h e two latter are those generally used a t present. T h e penetrometer has made i t possible t o control t h e consistency or as usually expressed, t h e penetration, within narrow limits. T h e penetrometers consist essentially of a needle of specified size (Roberts, KO. 2 ) fixed in a rod, t h e rod a n d needle being of, or loaded t o , definite weights. A clamp of some nature holds t h e rod with t h e needle, allowing t h e latter to penetrate as nearly as possible without friction. A device for measuring the a m o u n t t h e needle has penetrated after i t has been released for a specified t i m e a n d again grasped b y t h e clutch, is also necessary. T h e penetration is expressed in hundredths of a centimeter. Penetrations are most commonly made a t 2 5 ’ C. ( 7 7 ’ F.) with t h e needle loaded t o I O O grams penetrating for five seconds. I n order t o ascertain t h e extent a n asphaltic cement will harden when chilled t o o o C. (3 2 ’ F.),penetrations are frequently made a t this temperature with t h e needle loaded t o zoo grams penetrating for one minute. Occasionally i t is specified t h a t cements shall not show more t h a n a s t a t e d penetration a t 37.7’ C. (100’F). or 46’ C. (115’ F.), t h e needle being under a weight of 50 grams a n d released for five seconds. T h e Dow penetrometer frame consists of a base t o which is fastened a broad upright support with t w o shelves a t different distances from t h e base. T h e needle is held in a n aluminum rod weighted b y a rectangular frame of t h e same metal. T h e latter is fixed t o t h e rod a t about one-third t h e distance from its lower end. Weights are placed on t h e lower p a r t of t h e frame t o load t h e needle. T h e above-mentioned framework encloses t h e lower shelf on which is placed t h e sample. T h e rod passes through a hole in t h e upper shelf a n d is here grasped b y t h e clamp which is closed on t h e rod b y a spring when n o t penetrating. T h e rod a n d needle are released from t h e clamp b y pressing t h e spring together with a button-ended rod. T h e device for measuring t h e a m o u n t penetrated is fixed above t h e end of t h e rod. This consists of a rack, set vertically, t h e end of which can be brought down t o meet t h e t o p of t h e rod. This rack is i n gear with a pinion on a horizontal shaft. T h e latter passes through a graduated dial a n d a n adjustable h a n d is fastened t o i t there. A counterweight which hangs from a cord winding u p on a small pulley on t h e pinion shaft allows t h e rack t o be raised or lowered. T h e divisions on t h e dial correspond t o a movement of I/IOO cm. b y t h e rack.
