INDUSTRIAL A N D ENGINEERING CHEMISTRY
918
close to 5.04, that of sucrose. Lactic acid, acetone, p-oxybutyric acid, and ethyl alcohol have values very close to 4.85. Human and animal fats have an average energy value of 4.75, whereas that of the four acids used to standardize the oxycalorimeter and the calculated value for protein are all about 4.60. Table 11-Calorific
Vol. 17, NO. 9
Spectrophotometric Identification of Dyes‘*2 111-Basic Violets of the Triphenylmethane Group
Value of Various Substances
SV8STANCE Pure Substances: Sucrose Lactose Benzoic acida Salicylic acid’ Hippuric acid‘ Uric acid Commonly Metabolized Compounds: Starch Dextrose Lactic acid Animal fat Human fat Protein Acetone &Oxybutyric acid Ethyl alcohol Fuels: Anthracite coal Bituminous coal Coke Fuel oil Foods: High carbohydrate substances: Dried skimmed milk Oyster crackers Corn meal Nut bread Cheese sandwich Chicken sandwich Salmon salad sandwich Club sandwich Doughnut Highly nitrogenous substances: Glidine (vegetable protein) Ossein Collagen Plasmon Fats: Olive oil Corn oil Cottonseed oil Cod-liver oil Goose fat Butter Mixed foods: Beef stew Mince pie Animal foods: Hay, Specimen I Hay, Specimen I1 Cottonseed meal Linseed meal Gluten meal Excreta Human feces Steer feces a Correction for unburnt carbon necessary.
By Walter C. Holmes
Calories per liter oxygen 5.08 5.00 4.58 4.65 4.65 4 55 5.06 5.01 4.85 4.72 4.79 4.60 4.82 4.85 4.85 4.49 4.61 4.43 4.67 4.89 4.90 4.88 4.88 4.95 4.85 4.98 4.93 4.90 4.67 4.69 4.70 4.65 4.74 4.71 4.70 4.70 4.75 4.62 4.84 1.97 4.80 4.86 4.66 4.76 4.85 4.97 4.84
The fact that much of the food of man and practically all the food of domestic animals has a high carbohydrate content suggests that this value of 5.04 calories will play a large role in establishing the heat factors for other food materials and food mixtures. Although some apparent irregularities are seen in the values, in general the factor is not far from 4.6s for the rich nitrogenous substances, 4.70 for fats, and nearly 5.0 for those of a high carbohydrate nature. If one considers the average food of man and realizes that in determining the metabolism of humans from the oxygen measurements the calorific value of a liter of oxygen is commonly taken as 4.825, one can see that this average value would not be far from correct for all food mixtures, particularly if a composite sample of the total daily meals were taken. No doubt subsequent research will slightly refine some of these figures, but it does not seem justifiable a t the present time to refine a figure that is far inside the limit of accuracy possible in preparing the sample for combustion. According to advice from Paris the Manufactures des Glaces et Produits Chimiques de St. Gobain, important French manufacturers of superphosphates and other chemical products, plan t o increase their capital from 120,000,000 francs to 161,000,000.
COLOR
LABORATORY, BUREAU OF CHSMISTRY, WASHINGTON, D . C.
B
ASIC violets of the triphenylmethane class find important application as biological stains and therapeutic agents. An investigation has been made of all samples of these dyes which were available, in order to obtain such data as would afford a reliable means of differentiating between them. Samples of methyl violet (C. I. 6SO), crystal violet (C. I. 681), ethyl violet (C. I. 682), benzyl violet (C. I. 683), and gentian violet were examined. It is generally held that the gentian violets which have been supplied for biological staining have been mixtures of crystal and methyl violet, and the term will here be employed with that significance. It may be noted, however, that a sample of pre-war Griibler “Gentianaviolett” was found to be a typical methyl violet (of very low dye content) rather than a mixture of the type mentioned. Absorption in Dilute Alcoholic Solution
With dilute solutions of the dyes in question the absorption spectra in aqueous and alcoholic solutions are very similar. The decided tendency of aqueous solutions to dye the containing cells, however, makes it more convenient to carry out spectrophotometric measurements in alcoholic solutions. The data recorded in the first three columns of the table of constants, accordingly, were obtained with solutions containing 90 per cent alcohol. The measurements were made with a Hilger wave length spectrometer provided with a Nutting photometer. The approximate maxima of the bands (Column 1) were located with the usual technic, and the values were supplemented with determinations of the ratio of extinction coefficients a t wave lengths selected on each slope of the bands (Column 2). This type of ratio will frequently serve, as in the present instance, to establish a differentiation between similar spectra and to define the spectral locations of absorption bands more definitely than will the mere determination of maxima, particularly when the bands in question are somewhat broad and indefinite. Influence of Acidity
The dyes under investigation exhibit differences in stability to both hydrogen and hydroxyl ions. Ethyl violet is decidedly more stable to hydroxyl ions and less stable to hydrogen ions than the remaining dyes, which vary among themselves in only a relatively minor degree. The effect of acidity is more conveniently measured than that of alkalinity. The curves in Figure 1 illustrate the transition between the normal dye and its di-acid salt with increasing acidity in aqueous solutions of crystal violet. With aqueous solutions of the dyes the immediate modification of color and absorption which is brought about by the change in hydrogen-ion concentration is followed by a gradual decolorization, due to a process of increasing aggregation of dye molecules. I n alcoholic solutions more acid is required to produce an equivalent effect and the resulting 1 Received
May 8, 1925. Contribution No. 106 from the Color Laboratory, Bureau of Chemistry, Washington, D . C. . 2
*
I N D U S T R I A L -4SD ESGINEERING CHEMISTRY
September, 1925
solutions are stable. The values in Column 3 of the table are spectro-photometric ratios, which record acidity effects with the various dyes in 90 per cent alcohol. L6
i
I
I
A
~
The recorded variation in constants between different samples of methyl violet is less than was expected. A sample labeled “2B” proved to be indistinguishable from a second sample (of another company) labeled “R.” It is apparently indicated that the market supply of methyl violet is reasonably uniform in composition. It is probable that products will be encountered occasionally, however, which contain appreciable amounts of lower homologs or of fuchsin. Sample
1
2 3 4 5 6 7* 8* 9* 10* 11 12 13 14* 15* 16* 17* 18*
19 20*
21
* Starred
1
I
e 3
so
1
I
59??5? m8
I 620
I
660
I
919
T a b l e of C o n s t a n t s (Figures in p p ) 1 2 3 Methzd Violet (C. I . 680)
583 583 583 583 584 584 584 584
-
0.80‘ 0.97 0.82 0.97 0.84 0.96 0.80 0.95 0.86 0.97 0.85 0.97 0.96 0.84 0.88 0.97 Gentian Violet 587 0.96 0.94 588 0.95 0.93 Cryslal ViOlPl (C. 681) 0.90 590 1.06 0.90 591 1.08 591 1.07 0.88 ’ 0.90 1.08 591 0.92 1.09 591 1.08 0.91 591 1.08 . 0.89 591 0.90 591 1.08 Benzyl Violet (C. 683) 591 1.04 0.93 591 1.04 0.92 Ethyl Violet (C.I . 682) 595 1.12 0.65
4 0.94 0.94 0.94 0.95 0.94 0.95 0.96 0.95 0.96 0.96 0.97 0.96 0.97 0.97 0.97 0.96 0.98 0.97 1.14 1.15 1.79
samples were marketed as biological stains and unstarred samples aq textile products. The second sample of gentian violet was made by combining equal proportions of methyl and crystal violet a t this laboratory.
Figure I-Crystal Violet. Concn. = 10 mg. p e r l i t e r (1) = distilled water (2) = 0.01% (3) = 0.05% H2SO.r (by volume) (4) = 0.10%
i
1.5
Absorption in Concentrated Aqueous Solutions
All the dyes under investigation undergo radical alterations in absorption spectra with change in concentration in aqueous solution.3 The degree of dilution required to bring about the transition between the absorption band given by the dye in concentrated aqueous solutions and the band characteristic of dilute solutions, however, varies with the different dyes. This variation is illustrated in the curves of Figure 2, which record the absorptions of typical dyes in aqueous solutions of relatively considerable and approximately equivalent dye content. At the dilution employed ethyl violet shows merely an incipient development of the absorption band which is deTeloped by further dilution, and the transition with benzyl violet is appreciably less advanced than is the case with methyl’and crystal violets. The constants recorded in Columns 1 to 4 in the table are as follows: 1-The approximate spectral location (in millimicrons) of the absorption maxima in solutions containing 5 to 10 mg. of dye per liter of 90 per cent alcohol. ?--The ratio of E a t 600 pp to E a t 575 pp in the same solutions. 3-The ratio of E a t 590 pw in the same solutions to E a t 590 pw in solutions of the same dye content and alcoholic content ‘containing 0.85 per cent (by volume) of concentrated sulfuric acid. $-The ratio of E a t 540 pp to E a t 580 pp in aqueous solutions of the dyes of such Concentrations that E a t 540 is approximately 1.5when measured in a layer of solution of 0.0432 cm.
The second constant is of particular value in differentiating between methyl, gentian, and crystal violets, and the fourth constant is indispensable in distinguishing between crystal and benzyl violet. 3
Holmes, THIS JOURIAL, 16, 35 (1924).
I.0
0.5
-
-
Figure 2
Reduced Import Duty on Naphtha Distillates-Upon-the recommendation of the Finance, Trade, and Industry Commission of t h e Latvian Parliament, a new scale of import duties on petroleum products has been adopted. These new duties affect naphtha, distilled but not purified, kerosene, and photogen; benzine, naphtha-ether, gasoline, ligroin, and the like; solar oil, paraffin oil, and lubricating oil.
