Apr., 1917
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colored by normal milk allowed t o “age” under ( I ) T h e germicidal properties of formaldehyde i n relation t o microorganisms found in milk are shown ordinary conditions of temperature for 24 t o 48 hrs. in a general way. (3) Pasteurization increases t h e time required for ( 2 ) Unless i t be proven t h a t reductase is formed t h e decoloration of t h e reagent. within t h e milk by purely chemical changes, this (4) I n general, no proportionality exists between series, considered in relation t o t h e foregoing series of t h e time required for t h e decoloration of t h e reagent a n d tests, points t o t h e conclusion t h a t reductase is of t h e number of bacteria in milk. I n a given sample, bacterial origin, as t h e time required for decoloring however, a general relation seems t o exist between t h e t h e reagent was not reduced b y allowing t h e milk two up t o a given point of acidity. t o “age,” owing presumably t o t h e fact t h a t bacterial ( 5 ) Inasmuch as there is no absolute parallelism growth in t h e samples of milk was inhibited b y t h e between number of bacteria present in milk and t h e formaldehyde. time required t o decolor t h e reagent b u t t h a t t h e re(3) T h e partial decoloration which occurred at first , lationship seems t o exist in a given sample of milk, was probably effected b y t h e reductase present in t h e i t would indicate t h a t reductase is of bacterial origin milk before t h e formaldehyde was added. T h e final b u t t h a t not all bacteria found in milk produce this loss of power of these same samples t o effect t h e same enzyme. (This latter conclusion is in accord with reaction suggests t h a t t h e formaldehyde may interact t h e views of Fred.’) with t h e reductase or counteract its influence in some (6) It seems probable t h a t formaldehyde either way. T h e fact t h a t both of these substances are gradually retards t h e action of t h e reductase or destrong reducing agents does not t e n d t o render t h e stroys it. This is a matter, however, for more careful problem more easy of solution. investigation in t h e future. Since t h e completion of this work t h e report of It will be noted t h a t although t h e conclusions formut h e investigation of Harris a n d Creightonl on t h e lated in this paper are not in accord with t h e entire influence of certain poisons on reductase has appeared. body of conclusions of a n y previous worker in this Although t h e list of poisons reported b y t h e m as either field, yet many of t h e m are in close agreement with destroying t h e reductase or retarding its action does certain conclusions of a number of investigators. n o t include formaldehyde, t h e latter may act in a HYGIENIC LABORATORY similar manner. This, however, will be a matter for CARNEGIE HALL OF CHEMISTRY future investigation. ALLEGHENY COLLEGE. MEADVILLE, PA.
____~__
GEXERAL SUMMARY
I-A brief outline has been made of t h e classification, distribution a n d reactions of certain enzymes ; t h e possibility of making their sensitiveness t o various physical a n d chemical agents t h e basis of methods for determining t h e sanitary condition of certain foodstuffs has been considered. 11-A survey has been made of t h e work done concerning t h e source, nature a n d action of reductase in its relation t o certain methods which have been proposed for t h e differentiation of pasteurized\ milk from raw milk. 111-The experimental investigation undertaken by t h e authors of this paper has been described. As t h e result of this work certain conclusions have been formulated. T h e y are as follows: ( I ) Methylene blue as i t occurs in Schardinger’s reagent, F. M., is not decolored b y : ( a ) Normal fresh milk in less t h a n 20 min. When decoloration was effected in I O minutes or less time t h e milk was found t o contain I,OOO,OOO or more, microorganisms per cc. ( b ) Milk pasteurized at 70’ C. for I O min. unless approximately 48 hrs. have elapsed since t h e milk was pasteurized; or until t h e bacteria have had time t o multiply sufficiently. (c) Old milk i n which t h e “preservative,” formaldehyde, has inhibited t h e growth of bacteria. ( 2 ) Schardinger’s reagent, F. M., is as a rule de-
’ Harris and Creighton, J. Bid. Chem., 22 (1915), 535.
A STUDY OF THE VOLUMETRIC OR PEMBERTON METHOD FOR DETERMINING PHOSPHORIC ACID, WITH SOME EXPERIMENTS SHOWlNG THE INFLUENCE OF TEMPERATUFCE AND THE SULFURIC ACID RADICAL ON RESULTS* By PHILIPMcG. SHUSY Received October 20, 1916
There has been a great deal written a n d said of t h e volumetric method for determining phosphoric acid, b u t still many chemists have trouble in its use a n d manipulation. It has been found by most workers who employ this method t h a t a number of years of careful a n d patient experience is necessary t o master it, a n d owing t o t h e length of time necessary t o acquire this, many chemists have discarded i t altogether. The writer has h a d more t h a n I O years of practical a n d constant experience in determining phosphoric acid b y this method, both with a large fertilizer concern, a n d in t h e phosphate fields of Florida, and possibly some points already mentioned can be emphasized in this paper. On account of t h e extreme delicacy of t h e method, a n d in order t o show how i t may be rendered accurate a n d reliable, i t might be of interest t o include some experiments showing some of t h e principal causes t h a t bring about disturbances in results. T h e problem is most interesting, a n d while no pretense is made t h a t this article will cover t h e entire field, i t is hoped t h a t it will a t least serve t h e purpose of aiding 1 Ccntr. Bok;. Parasilenke. I I Abt., 35, 491. 3 Presented at 53rd Meeting of American Chemical Society, New York City, September 25 to 30, 1916.
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
;68
\
Vol. 9, No. 4
TABLE I-RESULTS BY VARIOUS METHODS OF TREATMENT 1-By dissolving in nitric acid and a few drops of hydrochloric acid. &By making solution according t o (2), and then adding barium chloride to remove sulfuric acid. 2-By adding a n equal weight of 50' Be. sulfuric acid, as in the manufacture of acid phosphate, and then making solution like (1). 7 and E-Solutions corresponding t o (1) and (2), respectively, only using 3-By adding twice the quantity of sulfuric acid, as is usually ema standard t h a t has been used in the writer's laboratory for the past 5 ployed in the manufacture of acid phosphate. years, and which contains much less iron and alumina than the A. C. S. +By solution in a mixture of 10 cc. sulfuric and 15 cc. nitric acid. Standard, but which, by coincidence, contains practically the same amount 5-By increasing the .sulfuric t o 25 cc. of phosphoric acid. CUBIC CENTIMETERS STANDARD SOLUTION SODIUM HYDROXIDE REQUIRED -CORRECTIVE FACTORSNo. 5'C. 20OC. 3OoC. 40' C. 5 0 0 c. 65" C. 5'C. 20'C. 30'C. 4OoC. SOo C. 65O C. 1 30.08 30.15 30 25 Av 30.22 Av 30.65 Av 31 15 Av 1.0023 1.00 0.99905 0.99472 0.9837 0.96573 30:10 30.'17 30.30 30:31 30.65 30.65 31 30 31 .'22 32.15 30.70 Av 31.10 Av 2...*, 30.20 30.0 $230 30.75 30.'72 30.95 131 .'02 0.998 1.005 0.99505 0.98144 0.97195 0.9375 32.20 31 30 Av 2B. . . . . . . . . . . . . . . . . . . ...... ...... 0.9611 3 1 45 3 1 .'37 32.75 Av. 0.9648 0,92005 31.25 Av. 3. 31.25131.25 32.80 32.77 31 40 Av 0.99802 0.99802 0.98529 0.96914 0.95866 0.95866 4 30.20 30.20 30 50 Av 3 1.15 A; 31 :40 Av. 30:70]30..60 31.08 31 11 31 50 31.45 3 1: 5 0 31 :45 31 45 Av 1.00166 1.00166 0.9895 0.9722 0.9648 0.96326 30.10 30.10 30 40 Av 30.95 Av. 31.25 Av. 5 30: 5 5 30 .'47 31.08 3). 01 31.28 3 1.26 31: 15 31.'30 31.00 0.9934 0.99011 0.98852 0,97258 6 30.35 30.45 30.50 30.35 Av 30.80 A". 7. 30.85 0.99108 0.97244 30.20 30.'27
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some chemists, and more particularly those starting out in making analyses of fertilizers, a n d of the materials which enter into their composition, and show t h a t when properly handled t h e method is equally accurate, or more so, t h a n t h e Standard Gravimetric. Dr. F. B. Carpenter, in his very able article, mentions both t h e advantages a n d disadvantages of the method, together with details which cause disturbances of results.' As a means toward more accurate determinations, a number of modifications of t h e original method have been proposed. Briefly stated, their principal features are as follows: I-Richardson's modification for analyzing acid phosphate, which depends upon t h e removal of sulfuric acid with barium chloride, after making solution in a mixture of nitric and hydrochloric acids.2 a-Separation of t h e phosphoric acid from sulfuric acid by precipitation with ammonium hydroxide, then, after filtering and washing, the phosphates are dissolved and precipitated in t h e usual way. 3-Fairchild's modification making t h e end-point sharper by t h e addition of barium chloride, after dissolving t h e precipitate of ammonium phosphomolybdate in a n excess of standard alkalia3 It is conceded b y those experienced in t h e method t h a t t h e details which have t h e greatest influence on results are temperature and t h e amount of sulfuric acid radical present; and t o show t h e effects of these important factors on t h e results, several series of experiments have been made which may be briefly described as follows: T h e sample of phosphate rock which was adopted by t h e Fertilizer Division of the Society as a standard for phosphoric acid was taken as a basis for the experiment^.^ The value of t h e standard adopted is 30.15 per cent, which was t h e average of a large number of determinations by t h e gravimetric method. After weighing out I-g. portions and putting t h e m into 200-cc. flasks, which had previously been 1 THISJOURNAL, 2 (1910). 157. 2 Sutton's "Volumetric Analysis, "Schimpf's "Volumetric Analysis," and J . A . C. S., 29, 1314. 8 THISJOURNAL, 4 (1912), 520. 4 "Details of Analysis for Standardization," THIS JOURNAL,S (1911), 118.
I
32.10 Av. 32.20 32.15
..........
....................
....................
0.96618
0.93312
carefully calibrated, solutions were made according t o t h e descriptions given in Table I. After making up solutions t o mark, and filtering through dry filters, aliquot portions representing 0.I g. were taken for analysis. After diluting with water t h e medium for precipitation was regulated in t h e usual way, by first adding ammonia until alkaline, and then clearing up by the addition of nitric acid. Before making precipitations from Solutions 4 and j I O g. of ammonium nitrate were added, as otherwise the precipitation would probably be incomplete in t h e presence of such a large quantity of sulfuric acid. As an experiment, I O g. of ammonium nitrate were also added t o ( a B ) . I n all other cases, however, no ammonium nitrate was added, other t h a n t h a t formed Erom t h e reaction between ammonia and nitric acid in getting t h e proper medium. With t h e precipitant a t 30' C., precipitation was made a t various temperatures as follows: At S o C. bv addinn 5 0 cc. Molvbdic solution. stirrine 30 min.
Filtering a n d washing was done by t h e use of 11 cm. filter papers: this t h e writer regards as being more accurate t h a n filtering under pressure, and when running a batch of 6 or more determinations a t a timeitis done about as rapidly. The precipitates were all washed free of acid as determined by t h e addition of a drop of N / 4 alkali t o t h e filtrate. I t is noteworthy t h a t in making these experiments only a or 3 of t h e duplicate determinations were r u n a t the same time, and therefore t h e results are more truly checks t h a n had all been duplicated together. Results found by precipitating a t t h e low temperatures, j and 20' C., were not duplicated through lack of time, but as would be expected, t h e figures agree closely when making precipitation from t h e various solutions a t these temperatures. As the strength of t h e standard solutions was practically 0.3238 I?, and as 0.1 g. of rock was taken for analysis, the number of cc. of solution required should
Apr.3 1917
T H E J O U R N A L O F I N D U S T R I A L AAVD E N G I N E E R I N G C H E M I S T R Y
very nearly correspond t o t h e actual percentages, provided there were no disturbing elements t o offset t h e results. I n Table I is shown t h e number of cc. required when precipitation was made at t h e various temperatures a n d from t h e various solutions and t h e corrective factor for each cc. I t will be noticed what a great deviation there is i n t h e number of cc. of t h e standard solution required t o dissolve t h e various precipitates formed under t h e different conditions of temperature, a n d t h e varying amounts of sulfuric acid, a n d t h a t according t o t h e Official Volumetric Method' t h e number of cc. required corresponds t o the percentage for anything from room temperature u p t o 6 j ', without making any allowance whatever for correction. While in t h e Official Method i t is not recommended t h a t sulfuric acid be used in making solutions of t h e material, no distinction, however, is made in t h e mode of precipitation, whether or not the sulfuric acid radical is present. It is noteworthy t h a t at a temperature of 65' C., much higher results are found on acid phosphate dissolved in nitric acid t h a n when phosphate rock was dissolved in a mixture of sulfuric acid a n d nitric acid. By reference t o t h e table under Treatment 2 , i t will be noticed t h a t t h e number of cc. of s t a n d a r d alkali required t o dissolve t h e yellow precipitate, when precipitation was made a t t h e various temperatures, varies all t h e way from 30 t o 32.16 cc., a maximum variation of 2.16 cc., which would correspond t o 2.16 per cent when not making correction. If we consider t h a t t h e addition of I g. of sulfuric acid t o I g. of rock gives 2 g. of acid phosphate, a n d t h a t t h e aliquot taken represents 0 . 2 g., t h e maximum variation caused by changes in temperature is 1.08 per cent, without correction, a n d when precipitating at 6 j " in determining t h e phosphoric acid in acid phosphate, results will often be I per cent higher t h a n t h e y should be. It was found in making t h e experiments t h a t there was much difficulty in making results agree when precipitating at j o a n d 6 j O , while a t 30 a n d 40' there was not t h e least trouble in this respect, t h e results being extremely regular. The deviation in analysis of phosphate rock caused b y changes in temperature, as shown under ( I ) , is about half of what it is after t h e addition of sulfuric acid (after t h e manner of making acid phosphate), t h e maximum variation being 1.14 cc. Experiment 3 shows t h e variation at j o a n d 65' after adding double t h e amount of sulfuric acid, as is usually employed in making acid phosphate. This addition gave a result 2.62 per cent too high, a n d 0.61 per cent higher t h a n results shown in ( 2 ) , necessitating a corrective factor of 0.92005 per cc. when precipitation was made a t 6 j " . Experiment 4, in which solution was made by dissolving in a mixture of sulfuric and nitric acids, shows a variation a t different temperatures of 1.2j cc., a n d with precipitation at 30, 40 a n d 50' C., t h e volume rei
Bureau of Chemistry, Bull. 107 (1912).
369
quired was from 0.3 t o 0.6 cc. greater t h a n in t h e acid phosphate under (z), b u t a t 65' this quantity was 0.71 cc. less. It was found t h a t by increasing t h e amount of sulfuric acid used in making solution t o 2 j cc., little, if any, difference was made in results. Experiment 6 shows t h e analysis after removing t h e sulfuric acid radical with barium chloride. The results were not duplicated, b u t they agreed closely with those under ( I ) , in which no sulfuric acid is added. Experiments 7 and 8 were made t o determine whether or not iron a n d aluminum h a d a tendency t o affect results, t h e sample being very low in these metals, while t h e A. C. S. standard is very high. The results were concordant. T h e results found a t t h e various temperatures and from t h e various states of solution show how utterly impossible i t is t o do correct work when precipitation is made a t from 40 t o j o or from 60 t o 65', as mentioned in t h e Official Method, unless correction is made b y t h e use of a standard, which is r u n along with t h e batch under identically t h e same conditions, a n d t h e n corrections made accordingly. If work is being done on acid phosphate, i t is suggested t h a t a control test be carried on at t h e same time by adding t o a weighed quantity of standard phosphate rock t h e amount of sulfuric acid used in making t h e acid phosphate. It was also found b y experiment t h a t t h e sulfuric acid may be added after making solutions in nitric acid with t h e same results. This suggestion is intended particularly for those who precipitate phosphoric acid at temperatures higher t h a n 30' C. It is advisable, too, that a stirring machine be employed. Should a sample of fertilizer under examination contain a large amount of organic matter like fish scrap, ground tankage or cottonseed meal, i t is suggested t h a t t h e method of solution be t h e addition of a mixt u r e of I O cc. sulfuric acid a n d I j cc. nitric acid, boil on a hot plate until black, a n d then oxidizing t h e organic matter by t h e addition of potassium nitrate. Whenever employing this method allow t h e flask t o cool down with t h e hot plate, otherwise i t will crack; then boil with about I O O cc. of water. A portion of a standard sample of phosphate rock is dissolved a n d treated in t h e same manner, a n d t h e value per cc. found a n d correction made. It is advisable when precipitating from a sulfuric acid solution t o add a t least j g. of ammonium nitrate. I t has been found also t h a t t h e age of t h e molybdic solution may seriously affect results. If a solution is very old a n d shows a tendency of separating out molybdic acid, i t should be discarded a n d not even mixed with a fresh solution. By keeping t h e solution in a dark bottle a n d in a cool place it will be preserved longer. A precipitating vessel t h a t is most convenient is a 2 5 0 cc. Soxhlet fat extraction flask fitted with a No. 9 rubber stopper; after adding a n excess of standard alkali, t h e stopper is inserted, a n d t h e flask shaken until t h e yellow precipitate is dissolved. The end-point is sensitive t o a drop, and therefore Fairchild's modification is unnecessary.
Vol. 9, No. 4
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
3 70
I n conclusion i t may be stated t h a t with a knowledge of t h e method a n d with strict attention t o detail, very accurate and reliable results may be obtained, and t h e fact t h a t i t is extremely delicate is a point in its favor. Accuracy, however, will come only with practice. LABORATORY OF
SAVANNAH
GUANOCOMPANY
SAVANNAH, GEORGIA
THERMOCLINE STUDIES AT KENSICO RESERVOIR' By FRANK E. HALE AND JOHN E. DOWD Received September 30, 1916
The new and enlarged Kensico reservoir is the storage reservoir for the new Catskill water supply nearest t o New York City. Owing t o t h e progress made on t h e dam, t h e reservoir was filled in t h e winter of 1915-16. Close watch was kept of t h e quality of t h e water in order t o utilize it a t t h e earliest possible moment. During construction t h e water of t h e Bronx watershed had been held back b y t h e Bronx a n d Rye Dykes and the Bronx supply fed from Rye Dyke. As soon as t h e quality of t h e water permitted, change of draught was made t o t h e new dam a n d filling continued over t h e Dykes in order t o conserve in t h e Catskill system as much of t h e winter and spring flow as possible. The problem was interesting in t h a t it is not t h e usual procedure t o use water from a reservoir without long standing and possibly blowing of bottom water after stagnation. TREATMENT OF RESERVOIR BOTTOM
Soil stripped from certain designated portions was used for filling areas of shallow flowage. Swampy areas were covered with sand and gravel t o a depth of 1 2 in. or more. The bottom and a margin of about 30 f t . outside t h e flow-line were cleared of all buildings, fences, trees, bushes, logs, stumps, high grass, tussocks or clumps of roots of bushes or grass, weeds a n d rubbish. Stone walls within t h e 30-ft. margin and t o a depth of 20 f t . below t h e flow-line were removed.
anything approaching t h e stagnation of summer is avoided. Water first flowed in from t h e Ashokan tunnel on November 2 2 , 1915,a n d continued steadily until January ~ j 1916, , when t h e water was 1 2 3 f t . deep. Filling was resumed February 21, 1916, and continued t o full reservoir level which was reached May 23, 1916. The water entering was of low turbidity and free from B. coli in I O cc., having seen long storage a t Ashokan reservoir. The water as it entered the reservoir stirred up the mud of t h e bottom with t h e result t h a t the whole volume of water in Kensico reservoir was muddy and showed B. coli in many of t h e tests in 0.1 cc. The turbidity contained fine silt which settled very slowly. The turbidity was still 30 p. p. m. a t t h e end of a month and naturally cleared more slowly in t h e deeper water. B. coli results improved with subsidence of turbidity and time of standing, tests in only I O cc. being obtained a t t h e end of 3 weeks and a t t h e end of 6 weeks being negative in I O cc. Special inspections were started by t h e Laboratory Division of t h e Department of Water Supply, Gas a n d Electricity, and special samples were taken on December 2 2 , 1915. Eight samples taken a t different points along the side of the reservoir had an average of only 36 bacteria per cc. (agar 3 7 ' C.) and no B. coli in I O cc. within 24 hrs., lactose bile test. I n 3 days' time t h e tests in I O cc. were positive in s/d of t h e samples. One only gave a test in I cc. These results proved t h e presence of attenuated B. coli only, its source being t h e disturbed mud of t h e reservoir. A p a t h was broken through the ice t o a point several hundred feet back of t h e intake a t t h e dam and samples taken f r 0 m . a row boat a t t h e surface and a t 50 ft. depth, the total depth of water being 82 f t . These samples were taken, as were all similar samples later, by t h e method employed for collecting dissolved oxygen samples, i. e . , allowing a larger bottle t o fill through a small bottle so t h a t t h e analysis of t h e water in t h e small bottle represents the actual conditions a t t h e
TABLEI-QUALITY OF WATERAT VARIOUSDRPTRS,KENSICORESERVOIR PHYSICAL CHEMICAL ANALYSIS 0 (Parts per Million)
EXAMPATION
."*E
s
Y
.*8 DATE Dec .22. 1915 Jan. 7, 1916
PLACE OF COLLECTION Surface 50 ft. Depth 82 ft. Bottbm 5 16 2v 34 Surface 25 ft. Depth 34.5 5 16 2u 4 16 2v 50 ft. Depth 35 117 ft. Bottom
.. . 0.116 0.038 0,002 0.15 0.106 0.024 0.002 0.15
8 2.2
6
u
gu
d 4 t
i
e
P
a d d
d
14 0.70 0.9 91.9 13.08 14 0.60 0.9 90.0 12.67
0.088 0.016 0.002 0.15 48 1.0 25 0.088 0.020 0.002 0.10 51 1.2 20 0.090 0.030 0.002 0.20 59 1.4 20
13.25
1 Presented at the 53rd Meeting. American Chemical Society, New York City, September 25 to 30, 1916.
Bact'l Mic'l
P
25 1.5 25
Designated areas within the 30-ft. margin a n d t h e reservoir bottom t o a depth of 35 ft. below t h e flowline were grubbed of stumps a n d roots. Material was burned, excrement removed, a n d chloride of lime used. T h e time of filling t h e reservoir was well chosen, late fall, since circulation continues all winter and
EXAMINATION
OXYGEN
13 0.40 0.4 93 13 0.50 0 4 13 0.50 0:4 92'
1i:25
Bacillus
coli ti$ad 0.1 in in in 1.0 10 p1
CC.
cc. cc.
15 0 0 0 37 0 0
+
15 15
1 1 0 0 0 20 1 1 0 0 0 100 0 1 9 0 0 0
depth sampled. These samples were given complete analysis, physical, chemical, bacteriological, and microscopical. Dissolved oxygen and free carbonic acid were also determined a t the reservoir. The results are shown in Table I. The temperature, oxygen-free carbonic acid and other determinations proved t h e water t o be of uniform character throughout. Microscopic organisms were practically absent, oxygen was abundant, 90
