Apr., 1916 INFLUENCE
T H E J O C R N A L OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY SPECIFIC
OF
GRAVITY
OF
LIQUID
01;
sTRENGrH-Alteration i n t h e specific grdvity of a dental cement liquid may be occasioned b y t h e addition or subtraction of water. I n actual practice, carelessness in capping t h e liquid bottle will result CRUSHING
15195
IS375
15915
I5980
SPECIFIC CRRVITY OF LlPUlO R‘T IS’C
CH4RT
VI1
in evaporation of water, t h u s increasing t h e specific gravity of t h e liquid. Chart VI1 shows t h e influence of specific gravity of t h e liquid on t h e crushing strength of silicate No. I . It will be noted t h a t a certain specific gravity, in $his case I . 5 5 7 j a t I j 0 C., gives t h e highest crushing strength, and t h a t a decrease ( a n addition of water) or increase (abstraction of water) results in diminished resistance t o sali.\-a. The importance of this observation is t h a t t h e method may b e utilized in determining t h e proper “balance” of a dental cement. The specific gravity of a liquid is an index of its concentration, a n d if t h e constituents of t h e liquid are properly proportioned with relation t o t h e powder of a dental cement, i t is possible t o “balance” t h e liquid b y determining t h e effect of a given liquid adjusted t o different specific gravities. It is evident from these results t h a t liquid of different settings, if supplied for use with one a n d t h e same powder of a silicate cement, would yield varying results as regards saliva resistance, a n d t h a t only one standard liquid can be expected t o yield t h e best results.
309
cement has no definite relation t o its ultimate properties, nor can a p r i o ~ iconclusions be drawn with reference t o t h e effect of a given constituent in a dental cement. This must be arrived a t experimentally. 11--A method for determining t h e crushing strength of dental cements is described i n detail. The conditions under which t h e tests are made have been s t a n d ardized so as t o conform, as nearly as possible, t o mouth conditions. 111-Crushing strength is of fundamental importance in establishing t h e relative value of commercial dental cements with respect t o their ability t o resist masticatory pressure. Tests conducted under saliva have a n added significance, in t h a t t h e effect of t h e saliva is incidentally determined. I\‘-Forty commercial dental cements were tested a n d found t o vary considerably in crushing strengths. Retrogression in strength under saliva occurred in a large percentage of t h e cements tested. There is no relation between germicidal efficiency a n d resistance t o saliva in t h e case of t h e copper cements. Those showing retrogression in strength in saliva m a y show either high or low germicidal efficiency. V-Several properties of dental cements, of importance in applied dentistry, may be studied with t h e aid of t h e a p p a r a t u s described in this paper. Further investigations relating t o t h e crushing strength of dental cements a n d other properties are being conducted in this laboratory a n d will be published in future papers. Acknowledgment is due F r a n k L. Grier for many valuable suggestions a n d aid in conducting t h e experimental work; also t o Paris T . Carlisle, 4th, for assistance in conducting t h e tests. LABORATORIES OF T H E L. D.
CAULK COXPANY
MILFORD,DELAWARE
COLOR STANDARDS AND COLORIMETRIC ASSAYS By H. V. ARXY A N D C. H. RING Received September 13, 1915 INTRODUCTION
SFTCIFIC CRRVITY OF LlOUlD RT 15-C
CHARTVI11
Reference t o C h a r t VI11 shows t h a t liquids higher in specific gravity t h a n t h e s t a n d a r d liquid do not show t h e characteristic loss i n strength in oil, although liquids of lower specific gravity show t h e same effect as i n saliva. Excessive concentration of liquid apparently results in increased solubility of t h e material with a corresponding loss in strength in saliva. S U MXA R Y
I-In order t o establish t h e “fitness” of a dental cement, i t is necessary t o consider, individually a n d collectively, its various physical, physiological a n d chemical properties. The composition of a dental
Entrusted b y t h e Committee on Revision of t h e National Formulary with t h e task of standardizing t h e coloring agents, cudbear a n d caramel, recipes for tinctures of which are given in t h a t book, one of us (in 1908) became interested in color standardization. Finding t h a t no rational system of color-matching obtained, other t h a n t h e Lovibond tintometer, t h e standard glasses of which are arbitrarily chosen, s t u d y suggested t h e use of a standard red solution made from a cobalt salt, a standard yellow solution made from a ferric salt, and a standard blue solution made from a copper salt. Such solutions were prepared, a n d b y mixing t h e three, blends were obtained t h a t gave a variety of hues limited only b y t h e character of t h e colors of t h e original fluids. This line of colored fluids, t h e “Co-Fe-Cu” blends-which were demonstrated a n d described a t t h e Eighth International Congress of Applied Chemistry1-gave a fine line of green, yellow a n d orange shades. b u t were lacking in deep blues and reds; so further work* 1
2
See Proceedings, Vol. 26, p. 319. A m y and Pickardt, Drugpisis Circular, 57 (1914), 131.
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310
was performed, in 1 9 1 3 and during the past year b y the present writers. The result of this work was the preparation of a supplemental set of colors, designated as t h e “Co-Cro-Cu’! blends. which furnish t h e needed blues and some of the reds. T o secure t h e purplish reds, blends of volumetric solutions of potassium dichromate and of potassium permanganate have been devised as indicated in Table I . These two
v01. 8, NO.4
and water; hence the preparation of the “Co-Cro-Cu” blends is merely a matter of mixing solutions t h a t can be kept in stock for months without deterioration. USE O F COLORED FLUIDS I N COLORISIETRIC
ASSAY
The article in the Druggists Civculav mentioned above showed t h a t the prescribed methods of colorimetric assays were far from perfect. This year, however,, we are able t o report t h a t practically every t i n t TABLE 1-SOLCTIONS U S E D F O R MAKING S T A N D A R D BLENDS STRENGTH desired in colorimetric work can be obtained f r o m NAME OF SERIES COLOR SUBSTANCES USED SOLVENT OF Formula Grams USED SGLCTIONS either t h e “Co-Fe-Cu,” the “Co-Cro-Cu” or the “Cro:Red CoCln.6H20 59.49 hlanganate” blends: and t h a t under certain conCo-Fe-Cu’, Yellow FeCla.6HzO 45 , 0 5 ditions the colorimetric assays themselves can be ! Blue CuS04.5HzO 62.43 1 Red CoCh 5XHs.H2O 2.8 Per cent made uniform. “Co-Cro-Cu” 2 Yellow (NH-one 0.1 3.0 1.8 None 0.7 5.0 1 . I . ? >-one n r 0.1 5.0 0.4 None 0 . 2
.BLE
the same color results as were obtained with t h e hydrochloric acid reagents and also seemed t o effect greater permanency in t h e tint. as is indicated in Table 8. We found t h a t slight variations in t h e amounts of reagents used made no perceptible differ-
+ +
+++
+ + +
++
T A B L E 9-COXPARATIVE LOVIBOKDREADISGS 2 OR 3 HOCRSAFTER h'lIXING I,'? HOIJRAFTER h1YIIXING hTITROGES CONTENT Red Yellow Blue Red Yellow Blue 1 : 3,000,000 5.0 2.0 1 5 -0.7 -0.2 5 . 0 - 4.0 1.5 -1.3 -0.7 1 . 5,000,000 5.0 1.6 -0.4 None 5.0 - 1.9 -04 None S o n e +0.4 4.0 None 7 - 0 . 3 1 : 10,000,000 4.0 1 : 12,000,000 3.0 -t 0.2 None + 0 . 2 I : 14,000,000 1.0 i- 1.8 T h e second readings were 1 : 16,000,000 1.0 1.5 IL-one identical with t h e first I ' 18,000,000 2 . 0 0.1 I : 20,0~0,0001.9 None 1 - 0 2
strengths can also he matched as closely as this, as far as Loribond readings are concerned, b u t , curiously, + these fluids of equal Lovibond values do not necessarily ++ + match when compared in Blake bottles. When so 1 compared the color quality does not appear t o 'oc the $: : I + same. for a peculiar tinge which i s characteristic ol the nitrite test is lacking in the "Co-Cro-Cu" blends. ence in t h e color results. also t h a t j o cc. G f the nitrite For practical purposes of analysis. hoivvever, these solution containing about half t h e quantity of reagents matches would be entirely satisfactory, h u t for es\vas always of t h e same color value as IOO cc. of t h e act work they left something t o be desircd: w e solved same solution containing t h e regular quantity of re- this difficulty by means of blends of the potassium peragents. LIaking Lo\-ibond readings of a few of t h e manganate and potassium dichromate standard coloretl stronger ,nitrite solutions, we found t h a t t h e strongest fluids. These blends are not a t all stable. ani!. as ones, particularly the one in which the nitrogen con- mentioned above. should be prepared freshly when needed. Preliminary t o matching the color of these tent was I : I,OOO,OOO, had t o be read n-ithin I ; or 2 0 min. after mixing. although the ones to which blends ivith the tints produced in the nitrite tests, both acetic and hydrochloric acids were added lasted we made Lo\-ibond readings of them as soon 6s possiblc after mixing. read them again on the follon-ing d a y , longer t h a n the others. To study the effect of time on the tint produced, and again on the third day. Table 11 t h r o m some light on the interesting charwe repeated the experiment. using the acidified A. P. H . h. reagent. \\-hicli we found the ,most satisfactory acter of these permanganate-dichromate blends. Beof the three. .Is solutions representing more t h a n cause of their instability. JTe have so far employed nitrogen I : 3 , 0 0 0 . 0 0 0 were not permanent in color t h e m only m-hen we found t h a t the "Co-Fe-Cu" after two hours. the solutions read had strengths or "Co-Cro-Cu" blends did not furnish the desired ranging from I : 3 , 0 0 0 , 0 0 0 t o I : zo.ooo,ooo. The shade of color. We hope, however, in t h e future to matching of t h e color of the nitrite tests with our study t h e m a t greater length. At this time we merely standard colored. fluids was not easy. since the color point out t h a t the results as shown in Table 11 provetl produced b y the addition of naphthylamine and sul- t h a t the blends required dilution before they would fanilic acid reagent t o a solution of nitrite is in a class match the tints of t h e nitrite tests. These dilutions
J
TABLE1 I-LOYIBOXD READINGSO E THE P E R h l A s C A ~ A T E - D I C H R O ~ . 4 T EBLENDS R E A D 2 D A Y, SA F T E K > f l X I S l : READ 1 D A Y AFTER M I X I K G READ S O O X AFTER hIIXING Yellow Yellow Blue Red Yellow Blue Red 2.0 1.6 -0 , 5 5.0 1.6 -0.5 0.i 0.1 5.0 -0.; 0 i 1.6 1.6 0.1 -0.5 1.0 0 . 1 4.0 j.0 0.7 - 0.1 -0.5 1 .0 0.7 i 0 I 4.0 1.6 --0 . 3 I .6 5.0 - 0 . 4 + 0 . 1 -0.2 1.6 0 .1 0 2 -0.3 2.0 0.1 5.0 5 . 0 i- 0 . 1 -0.1 2.0 0.1 4.0 -0.2 1.0 - 1.5 4.0 -0.1 1.0 1.3 0.2 1.9 T 1.0 -0.6 -0. I 2 . 0 i0.4 1.8 t 1.0 1 . 8 7 1 . 0 0.4 0 I 0.2 -0.6 -0. 1 3.0 t 0.2 2 . 0 1 . 8 t 1 . 3 1 . 9 i- 0 1 0.1 1.0 t 0 . i -0.4 0.1 -0.1 2.0 1.5 2.0 1.6 1.3 0.1 -0.4 4.0 0.4 0.7 0.7 -0.1 3.0 T 1.5 0.2 0.4 -0.2 0.1 None 5 ,0 5.0 . 7None 5.0 1 . 0 -0.1 +o. 1 5 . 0 I- 0 . 4 -0.3
+ +
+
+
+
+ + t
++
+ + +
+
-
+
+
-
++ + + ++ ++ +
-
Blue -1 0 --0 . T
--n, s
-0.7 - 0 . .3 ---0. 5 -0.4 -0.2 --0 , 1
-0, 3 Sone
Apr., 1916
T H E J O U R N A L O F IiVDLISTRIAL A N D ENGIIVEERING C H E M I S T R Y
31.5
were prepared b y first making a blend from N / ~ o o o which are designated as Nos. I , 2 a n d 3, in Table permanganate a n d N / r o o dichromate solution a n d 14. t h e n diluting t o t h e desired intensity of color. T h e TABLE1 4 - L O V I B O N D READINGSO F S O L U T I O N S OF THREE S A M P L E S OF VANILLIN Lovibond readings appear in Table 1 2 . Readings ~Z-LOVIBONDREADINGS O F “MN-CR” FLUIDS DILUTION Red Yellow Blue
TABLE
BLEND
taken Sample V A N I L L I N l/z HOURAFTER MIXING No. CONTENT Red Yellow Blue 1 1: 50,000 None 0.4 0.2 1.0 0.2 1 : 2 0 0 0 0 None 0 . 4 + 0 . 2 l . O + O . 2 2 1:50000 N o n e 0 . 4 + 0 . 2 1 . 0 + 0 . 1 1 : 20:OOO None 0.4 0.2 1.0 0.3 3 1:50,000 None 0.4 0.2 1.0 0.1 1: 20,000 Kone 0.7 1.5 0.1
+
+
+ +
+ ++
2 OR 3 Red None None None None r\;one None
HOURS AFTER MIXING Yellow 0.4 0.2 0.4+0.2 0.4+0.2 0.4 0.2 0.4 0.2 0.7
+
4
+
Blue 1.0 0.2 l.O+O.2 1.04-0.2 0.3 1.0 1.0 0.1 1.3 0.3
+
+ + +
Endeavoring t o see if solutions of three samples of equal strength would be of uniform color when all “‘35 3 0,g, 7” 1.6 A-one 0.1 were treated in t h e same manner, we carried o u t one 1.6 + 0.2 None 0.1 “40~0” 2.0 + 0.1 None 0.1 test of each solution i n t h e two strengths I : 50,000 “4577” 1 9 + 0 4 0.1 None “SOCl,” 1.9 + 0 7 None 0.1 a n d I : 20,ooo. I n each of these tests we used 4 “55 1 6 + 1.3 None 0.1 “607,” 1 8 + 1 5 + 0.1 -0.1 0.2 drops oE bromine water a n d I cc. of ferrous sulfate Since t h e dilutions of t h e “&In-Cr-15-1” blend solution, excepting in the last test. when we used 5 seemed t o us t o be t h e best matches for t h e t i n t pro- ’ drops of bromine water instead of 4. It is plainly duced in t h e nitrite. tests, we prepared four nitrite seen t h a t t h e vanillin tests produced uniformity of tests for final matches, using reagent No. I and ob- color, only when identical amounts of reagents were used, regardless of t h e amount of vanillin in solution. When tained t h e Lovibond readings given in Table 13. t h e amount of bromine water was increased b y only T A B L E 13-LOVIBOND READINGS A N D “MN-CR”MATCHES OF NITRITETESTS I drop, there resulted a n increase i n color value, as “Mx-C~-15-1” MATCHES is shown by reading of sample KO. 3, I : 20,000. 3-ITROGEN LOVIBOND READING 1st 2nd CONTENT Red Yellow Blue Observer Observer T h e five tests t h a t h a d been treated with 4 drops “30%” 0 . 1 “30’%” None 1 : 20,000,000 1 . 8 of bromine water a n d I cc. of ferrous sulfate solution 0 . 2 “35%” “35%” None 1 : 18,000,000 1 . 8 + 0 . 1 None “45%” 1 : 14000000 2 . 0 + 0 . 2 0 . 2 “40%:: were given t o t w o observers as “unknowns” for t h e Eone “55% “5.5%:’ 1.9 + 1.0 + 0 . 2 -0.2 1 : IO:OOO:OOO purpose of being arranged in t h e order of color intensity, Two observers independently matching as “unb u t as all h a d t h e same t i n t , neither observer could knowns” t h e colors obtained in these nitrite tests with tell which were t h e vanillin dilutions I : 20.0oo a n d t h e “1In-Cr-15-1” dilutions, both sets being in Blake which t h e I : jo,ooo. bottles, arrived a t t h e concordant results given in The effects of varying amounts of t h e reagents Table 13. were t h e n tested with t h e results given in Table I S , Comparison of Tables 1 2 a n d 13 show clearly t h a t TABLE I j - E p F E c T O F V A R Y I N G AMOUNTSOF REAGEXTS O N V A N I L L I N TESTS matches i n Blake bottles agree closely with those cc Drops FeSOI obtained b y t h e Lovibond method. Curiously. how- Bromine SOlU- SAORTLY AFTER MIXING 1 OR 2 HOURSAFTER MIXING Water tion Red Yellow Blue Red Yellow Blue ever, there is rarely a n gbsolute agreement between 1 : 20,000 VANILLINSOLUTION 0.2 0.7 + 0.1 1.5 1.6 None 0.7 5 1 them, although t h e difference is within t h e limits of 1.0 + 0.1 1.9 None 0.7 + 0.1 1.0 + 0.7 0.2 6 1 visual error. 0.7 1.0 + 0.1 1.9 + 0.2 0.2 None 1.0 + 0.1 2.0 7 1 I
I
VANILLIN
T e first tried t h e vanillin method given i n Bull. 1 0 7 , Bureau of Chemistry, C . S. Department of Agricult u r e ; it may be outlined as followS: Fifty mg. of vanillin are dissolved in 2 j cc. of alcohol a n d t h e solution is made u p to I O O cc. with water; this solution, therefore, contains I p a r t of vanillin in 2 , 0 0 0 . Two cc. of this s t a n d a r d are diluted with 30 or 4 0 cc. of water, 3 or 4 drops of bromine water added a n d enough freshly prepared ferrous sulfate solution t o produce a maxim u m bluish green color; thereupon enough water is added t o make a total volume Qf jo cc. This colored dilution, therefore, has a vanillin content of I : jo,ooO, a n d is supposed t o be of t h e same t i n t as a n y other vanillin solution of t h e same strength prepared in t h e same way. We tried several solutions of various proportions of vanillin, a n d also treated t h e m with varying amounts of reagents, b u t our experience with this test was highly unsatisfactory and we consider i t unreliable. We, therefore, confined ourselves t o tests b y this method of only two strengths of vanillin, I : jo,ooo a n d I : zo,ooo, preparing t h e solutions from three different samples of vanillin which were on h a n d a n d
1.6 None 0.7 5 2 0.~ 2 0.7 1.6 6 2 0.1 2.0 0.2 1.0 7 2 VANILLIN SOLUTION 1 : 50,000 1.o 5 1 None 0.6 1.o None 0.6 1.0 None 0.6 1.3 5 2 None 0.6 1.3 None 0.6 6 2 1.3 None 0.6 7 2
0.2 0.2 0.2
+
: ;
++ 0.1 + 0.2 0.2 + 0.1
None None 0.2 None 0.1 0.2
0.7 1.0 0.6 0.6 0.6 0.6
0.7 0.7
++ 0.1 0.1
1.5 1.0 2.0
+ 0.7 1.0 + 0.1 1.0 + 0.1 1.3 1.3 + 0.1 1.6 1.0 + 0.7
which show t h a t t h e intensity of color produced in t h e official vanillin test depends principally upon t h e a m o u n t of reagents used a n d not upon t h e amount of vanillin present. We, therefore, abandoned this method a n d turned t o t h e one proposed b y Folin. FOLIK’S VANILLIS AssAY-Directions for t h e preparation of t h e reagent used a n d for the manipulation followed in this assay were taken from THISJ O U R N A L , 4 (1912), 670, a n d m a y be outlined as follows: The phosphotungstic-phosphomolybdic acid reagent used is made b y placing in a flask with reflux condenser I O O g. pure sodium tungstate a n d 20 g. phosphomolybdic acid, followed by roo g. 85 per cent phosphoric acid a n d 700 cc. water. The mixture is t h e n boiled over t h e open flame during I*/* hrs. a n d is allowed t o cool, after which it is filtered, if necessary, finally diluting t o 1000 cc. with water. This solution has a vanillin content of I : 10,000. Five cc. of i t are placed
T H E J O U R N A L O F ILYDC-STRIAL AA-D E N G I l V E E R I X G C H E M I S T R Y
316
in a glaks-stoppered cylinder and j cc. of the phosphotungstic-phosphomolybdic acid reagent are added. After mixing well a n d letting stand for j min. t h e fluid is diluted t o j o cc. with a saturated solution of sodium carbonate. After standing far I O min., t h e blue color of the fluid, which contains I part of vanillin in IOO,OOO, is observed. We prepared standard solutions from two samples of vanillin. Each was diluted t o three different strengths representing I : I O O , O O O , I : ~ j o , o o o ,a n d I : zoo,ooo, respectively. When these solutions were tested a n d read with t h e tintometer (Table 16) we found t h a t t h e two original sanillin samples gave TABLE16-I,OVIBOKD READXKGS OF VASILLIN SOLUTION No. 1 CONTEXT Red Yellow Blue 1 : 200,000 0.3 0.2 2.0 1: 150,000 0.4 0.2 0.4 0.1 1.6 1.0 1: 100,000 1.0 0.7 0.05 3.0 0.7
+
++
++
FOLIP;VAWILLIN TESTS SOLUTION h-0, 2
Red 0.3 0.4 0.1 1.0
+
Yellow Blue 0.3 1.9 0.4 0.1 1.5 1.0 0.7 0.1 2.0 1.5
TABLE17-
READINGSOF N / 5 0 Red 0.2 0 . 2 4-0 . 1 0.2 0.1 0.2 0.1 0.2 0.1 0.4 0.3 0.3 0.3 0.3 0.4 0.4 0.1 0.4 0.1 0.2
+ ++
“3-3-10
’
++
+ +
++
’ 2-2- 10”
“CO-CRO-CU” BLENDS Yellow 0.2 0.2 0.2 0.2 0.2 0.7 0.2 0.2 0.3 0.3 0.4 0.4 0.1 0 . 4 -L 0.1 0.2
+
Blue 1.0 t 0 4 1.6 I .9 2.0 0.1 1.5 1.0 2 0 1.6 1.0 1.0 0.05 1.3 1.6 2.0 0.1 2.0 0.4 1.9 1.0 1.8
+ ++ + ++ +
Comparing t h e tests a n d t h e blends as “unknowns” in Blake bottles, we found t h a t t h e vanillin dilution I : IOO,OOO matched t h e “Co-Cro-Cu” blend “3-3-10, IOO~’,” that vanillin dilution I : 150,000 matched “Co-Cro-Cu” blend “2-2-8, 707’ ,” and t h a t vanillin dilution I : zoo,ooo matched “Co-Cro-Cu” blend “2-2-10, 607,.” Second readings of t h e vanillin tests are not given, since t h e color, after half an hour, was so changed t h a t t h e readings were worthless. Vhile t h e Folin vanillin test is more satisfactory t h a n t h e Official Method, it leaves much t o be desired. I n either test, a slight variation in t h e amount of reagent added makes too great a difference in the color t o permit it t o be an accurate method of analysis. We believe t h e Folin test for vanillin t o be a good one, b u t think it needs considerable experimental work before it can be called perfectly satisfactory. URIC ACID
After experimenting on several proposed colorimetric tests for uric acid we found t h e most satisfactory one was t h a t published b y Riegler‘ in which phosphomolybdic acid is t h e reagent employed. T h e standard solution was made b y adding 0.1 g. of Kahlbaum uric acid t o t h e same quantity of sodium bicarbonate and dissolving in water t o make a total volume of I O O cc. This represented a uric acid con12.
anal. Chem., 61 (1912), 466.
KO.4
tent oi I : 1,000. T h e test was carried out as follows: One cc. of t h e standard uric acid solution was mixed with 2 cc. of I O per cent solution of phosphomolybdic acid in a glass-stoppered cylinder; after mixing thoroughly, 7 cc. of j per cent solution of sodium phosphate were added and then t h e well mixed liquid was diluted with water t o make 30 cc., t h e uric acid content of the-finished fluid being I : 30,000. We also mad.e similar blue fluids containing uric acid, I : 40,000 and I : 50,000. The color produced in these tests was similar t o t h a t obtained in t h e vanillin tests, b u t much more permanent. I t \%-asno trouble t o obtain a second reading with the tintometer after t h e lapse of I hr. The results of readings are given in Table 18.
~~
the same color effects for equal strengths of dilution and t h a t the color produced was proportional t o t h e amount of vanillin present. We found excellent color matches for these tests in blends from our A 7 / j o “Co-Cro-Cu” standard colored fluids. These blends mere then diluted and examined in t h e tintometer with t h e results given in Table 1 7 . BLEKD “2-2-8”
Vol. 8,
TAELE18-LOv15OSD URIC ACID 1 : 50,000 1 : 40,000 1 : 30,000
Reading 1st 2nd 1st 2nd 1st 2nd
Red 0.2 0.2 0.2
0.2 t 0.1 0.4 0.1 0 . 4 -! 0.2
+
READINGS Yellow Blue 0,05 1.5 1.0 1 . 0 $- 0 . 1 0.1 1.3 0.1 2 . 0 4- 1 . 3 0.2 3.0 0.1 0.2 0.05 3 . 0 i1 . 3 0.2 0.1 4.0 0.1
++
++
+ +
Excellent color matches in Blake bottles were obtained for these tests with our standard “Co-Cro-Cu” colored fluids. T h e uric acid fluid I : jo,ooo matched our blend of “Co-Cro-Cu, 2-2-8, 8 0 ~ ~ 0 ; ”the one diluted t o I : 40,000 matched the straight N j j o blend of “Co-Cro-Cu, 2-2-8” without a n y dilution, while the one diluted t o I : 30,000 had greater intensity of color t h a n had the straight Ll‘t’jo blend. We, therefore, prepared dilutions from our AV/I O “Co-Cro-Cu” fluids and found a proper match for t h e uric acid I : 30,000 in a blend of “Co-Cro-Cu, 4-3-12, 307~,” prepared from the -4s noted in some of t h e other tests, exact matches, when the fluids were viewed in Blake bottles, were not t h e same as t h e corresponding Lovibond readings. For comparison therefore will state t h a t the Lovibond readings of the “Co-Cro-Cu” matches were: N/IO((4-3-12, 30C;~”--red 1.0 0 . 2 , yellow 0.4 0.1, blue 4 . 0 ; N / j o ‘ ‘ 2 - 2 2 - 8 : iooyc“--red 0.4,yellow 0 . 7 , blue 2.0 1.6; N / s o (‘2-2-8, 8o%”’--red 0.2 0.1, yellow 0 . 2 , b l u e 2 . 0 0.2.
+
+
+
+ +
SALICYLIC ACID
Colorimetric tests on solutions of salicylic acid were made according t o directions given in Bull. 107, Bureau of Chemistry, U. S. Department of Agriculture. The standard solution is prepared by dissolving 0.1 g. of salicylic acid in IOO cc. of water, this representing a salicylic acid content of I : 1,000;I cc. of this solution is placed in a glass-stoppered cylinder and is diluted with water t o 5 0 cc.; a few drops of ferric chloride solution ( 0 . j per cent) or ferric alum solution ( z per cent) are then added, and after mixing, t h e fluid takes on a bluish color suggestive of lavender. I n experimenting with this test, we found t h a t the ferric alum solution produced a deeper color t h a n did t h e same amount of ferric chloride solution. This was t o be expected, hornever, since a given amount of a 2 per cent ferric alum solution contains more iron per cent ferric chloride t h a n does t h e same amount of solution. I n comparing tests of equal strength where the amount of metallic iron in each reagent used was
T H E J O T R N A L OF I,VDCSTRIAL A N D ENGINEERING CHEMISTRY
Xpr., 1916
equal, we obtained equal color values. T o a solution containing salicylic acid I : jo,ooo we added 9 drops of 0.5 per cent ferric chloride solution a n d compared the resulting color with t h a t produced i n a solution of t h e same salicylic acid content t o which were added 4 drops of t h e 2 per cent ferric alum solution. T h e tints were exactly t h e same. Desiring t o determine t h e effects of various amounts of t h e ferric reagents on t h e salicylic acid reaction, Lovibond readings were t a k e n as shown in Table 19. TABLE EFFECT OF VARYINGREAGENTSON SALICYLIC ACID TESTS Salicylic Acid 1 : 25,000 FERRIC SOLN. Salicylic Acid 1 : 50,000
Reanent Drops Alum 4 4 Chloride 9 Chloride
Red Yellow 2.0 0.1 0.1 1.6 None 2 . 0 + 0 . 1 None
+
Blue 0.7 0.4 0.1 0.7f0.1
+
Red Yellow Blue 3.0 1.8 0.1 1.6 2.0 0.1 0.7 4- 0.1 3.0+1.8 0.1 1 . 6 4 - 0 . 1
+
Finding t h a t t h e color produced b y t h e ferric chloride solution was more permanent t h a n t h a t of t h e ferric alum solution, we thereafter used only t h e former. A s t a n d a r d solution was prepared from crystallized salicylic acid. A small q u a n t i t y of this was dissolved in I cc. of alcohol a n d t h e n diluted with water t o I : IO,OOO. From this a I : 50,000 solution was prepared a n d t o jo cc. of t h e latter 9 drops of ferric chloride reagent were added. T h e Lovibond reading of t h e resulting fluid was: red, 2.0 0.1;yellow, none; blue, 0.7 0.1,which is exactly t h e same reading as t h a t obtained from t h e s t a n d a r d solution of t h e other sample of salicylic acid, each test being of t h e same strength a n d treated with t h e same amount of t h e same reagent. As subsequent tests showed t h a t t h e minute q u a n t i t y of alcohol present h a d no effect on t h e color results, we suggest t h a t in preparing t h e salicylic dilution, t h e acid be dissolved in a small amount of alcohol, as directed above, in order t o facilitate solution. Two standard ferric chloride solutions of different strengths were t h e n prepared-N/Io a n d iV/ 2 0 a n d t h e colors produced on different volumes of salicylic acid solution I : j o j o o o gave Lovibond readings as per Table 20. These figures suggested t h e use of
+
+
TABLE 20 N/10 FERRIC CHLORIDE 1 cc. 2 cc. 1 cc. 2 cc.
in 50 ce. in 50 cc. in 100 cc. in 100 cc.
Red 2.0 2.041.9 2.0
Yellow None None None None
Blue 0.7 0.1 0.7 0.1 0.7 0.1 0.7 0.1
++ ++
N / 2 0 FERRIC CHLORIDE
Red 2.0 2.0 1.9 2.0
Yellow None None None None
Blue 0.7 0.05 0.7 0.1 0.7 0.01 0.7 f 0.05
+ ++
I cc. of N / I O ferric chloride reagent t o j o cc. of solution containing salicylic acid in tests of this kind, a n d we prepared t o match t h e colors with our “Coand Cro-Cu” N / 5 0 blends. Finding t h e “7-1-5” “6-1- j” blends t h e best matches, these were diluted a n d examined in t h e tintometer with t h e results given in Table 2 1 . Comparison of these results with those given in Table 19 shows t h a t t h e “Co-Cro-Cu” blends
TABLE~I-LOVIBOND R ~ A D I N OF G S12’/50 “CO-CRO-CU”BLENDS “7-1-5” BLEND DILUTION Red Yellow Blue 0.1 None 0.4 f 0.1 “ 60%:: 1.8 “6.5% 2 . 0 - k O . 1 None 0 . 4 + 0 . 1 “70%” 2.0 0.2 None 0.4 0.2
+
+
-+
“6-1-5” BLEND Red Yellow Blue 1.6 0.2 None 0.4 0.2 1 . 9 f 0 . 1 None 0 . 7 + 0 . 1 2.0 f 0.2 &‘one 0.7 0.2
+
+ +
“7-1-5,. 65%’’ a n d “6-1-5, 6 5%” have practically t h e same Lovibond readings as t h e colored fluids resulting from t h e salicylic acid dilution I : jo,ooo being treated with t h e ferric chloride reagent, a n d
317
t h e identity in color of these three fluids was further established b y matching as “unknowns” in Blake bottles. PHOSPHATES
We tried both phosphoric acid a n d sodium phosp h a t e with t h e regular ammonium molybdate reagent used i n qualitative analysis a n d studied t h e color produced. The standard phosphate solution repreT o j cc. of this sented a PzO5 content of I : 2,000. in a glass-stoppered cylinder were added 2 cc. of nitric acid a n d 4 cc. of a 5 per cent solution of ammonium molybdate a n d t h e mixture was t h e n diluted with water t o 50 cc. T h e finished fluid represented Pz06( I : zo,ooo), and t h e color obtained was a pure yellow t h a t was perfectly matched b y our N / j o ammoniacal dichromate standard fluid diluted t o “Ijglg,” i. e., t h e color of a mixture of 15 cc. of t h e N / j o ammonium dichromate standard fluid a n d 8 j cc. of water. The Lovibond reading of t h e PZOS solution ( I : 2 0 , 0 0 0 ) was: red, none; yellow, 1.0;a n d blue, 0 . 0 5 , while t h a t of t h e N / I O dichromate fluid (“Ij%”) was: red, none; yellow, 1.0;a n d blue, 0.05. Solutions having a P20s content of I : 10,000 were t h e n tried with t h e same reagents, b u t t h e resulting solution became cloudy within j min. We t h e n tried t h e test, using 4 cc. of nitric acid instead of z cc., b u t although t h e liquid remained clear, t h e color was lighter t h a n it was in t h e previous tests with solutions have a Pz05 content of I : 20,ooo. This is evidently another test in which exact quantities of reagent must always be employed. COLLEGEOP PHARMACY COLUMBIAUNIVERSITY, NEW YORK
THE GENERAL APPLICABILITY OF THE PAPER PULP FILTER TO QUANTITATIVE ANALYSIS’ B y S. L.
JODIDI
AND
E. H. KELLOGG
Received February 21, 1916
I n t h e course of a n investigation into t h e chestnut blight disease t h e authors have made a number of phosphoric acid estimations of various chestnut barks according t o Neumann’s method. The latter was shown t o yield somewhat inaccurate results because of t h e too low2 factor used for calculating t h e phosphoric acid, t h e inaccuracy being due in part t o t h e influence of t h e water3 used for washing t h e ammonium phosphomolybdate precipitate. Inasmuch as t h e difficulties encountered in t h e filtration and washing of t h e yellow precipitate on a folded paper filter, as recommended by Neumann, were successfully overcome b y t h e employment of t h e pulp4 filter which was also found suitable for t h e filtration of calcium oxalate5 a n d magnesium ammonium5 phosphate, i t was natural t o suppose t h a t t h e pulp filter may be generally applicable t o quantitative analysis. This is actually t h e case, as will be seen from t h e d a t a presented in this paper. 1
Published b y permission of the Secretary of Agriculture.
2S.L. Jodidi, J . A m . Chem. Soc., 37 (1915), 1708. * S. L. Jodidi and E. H. Kellogg, J . F r a n k . Inst., 180 (1915i, 349. S. I,. Jodidi and E. H. Kellogg, Biochem. Bull., 4 (1915), 87-94; see also J . A m . Chem. Soc., 27 (1905), 287. 5 S. L. Jodidi and E. H. Kellogg, J . Fvank. I n s / . , 181 (1916), 21;.
