INDUSTRIAL AND ENGINEERING CHEMISTRY
January 15, 1929
in absorbing power. It seems probable, however, that a modification of this method might be applied to other materials whose constituents differ less widely in absorbing power, provided the required sensitivity is not so high.
a X-RAY
TUBE
I
/LEAD
PROTECTIVE RESISTANCE SAMPLE CONTAINER
-
C A LVAN OMETER SHUNT
., SULPHUR INSULATOR
L---J
H.V.
IONIZATION CHAMBER
-
!
BATTERY OF 100 VOLTS
Figure 1
A diagram of the experimental arrangement is shown in Figure 1. All wires, batteries, and instruments were electrically shielded. A water-cooled molybdenum target diffraction type Coolidge tube, operating a t 35 kilovolts and 20 milliamperes, was found well suited for the work. The ionization chamber was of the Bragg type and the galvanometer was a Leeds and Northrup moving-coil type instrument with a sensitivity of 10-10 amperes. Specimen containers made from brass tubes having an inside diameter of 3.97 cm. with an effective length of 5.08 em. were found satisfactory. The capped ends contained 2.54 cm. diameter holes, over which 0.00508 cm. thick aluminum windows were placed. The standard solutions were made up from tetraethyl “fluid” of such a composition that 3 cc. of “fluid” contained
27
1.65 CC. of P b ( C Z H ~ ) Eight ~. samples were made up containing from 0.0 to 3 cc. of tetraethyl lead per gallon (3.7854 liters) using commercial gasoline as the solvent. Among the conditions which exert a marked influence on the shape of the curve will be the type of radiation and the thickness of specimen penetrated by the beam. Figure 2 shows two curves obtained under the above operating conditions. From these curves i t seems evident that: (1) The method holds distinct promise as an analytical tool; (2) the experimental conditions as outlined give practically straightline curves; (3) an accurate control of operating conditions is important. It was also observed that close current control is equally important, Among further refinements to increase the precision may be mentioned a high sensitivity resistance bridge in conjunction with an i o n i z a t i o n 4 chamber, or two ionization chambers bal- 2 a n c e d a g a i n s t each other, one for a standard specimen and the a 20 2 30 other for t h e “uncc known.” Figure 2 As the time required for each determination by this method may reasonably be anticipated t o be as short as 5 minutes, while the usual chemical method requires 40 minutes, a further practical and economic point is added to the value of this new method.
ti
I O
IS
CONC
Pb(ET)*PEI
CAL
Note on the. Estimation of Borate in Natural Waters‘3z Margaret D. Foster SURVEY, UNITED STATES GEOLOGICAL
I
N T H E examination of natural waters information on
the probable content of borates is sometimes desired. The Gooch m e t h ~ d involving ,~ the distillation of methyl borate, takes more time and requires more water than are usually available for the determination. It has been found satisfactory to use for such samples an adaptation of the wellknown qualitative test with turmeric. When all the details described below are followed carefully the results obtained are sufficiently accurate for the purposes of a general survey. Time has not been available to make a study of possible interfering substances or of the possibility that boron might be present in a form that would not react with the turmeric. It appears, however, that the quantity of borate in most natural waters is indicated fairly closely by the method described.
WASNINGTON,
D.
c.
has been repeatedly washed in water are dissolved in 500 cc. of alcohol. Filter before use. HYDROCHLORIC ACID SOLUTION-4 cc. of hydrochloric acid (sp. gr. 1.178-1.183) are added t o 96 cc. of distilled water. SALT SOLUTION-25 grams of sodium chloride and 25 grams of sodium sulfate (anhydrous) in 1 liter of distilled water. Procedure
Add 1 cc. of the hydrochloric acid solution and 1 cc. of the turmeric solution to 10 cc. of the sample in a small white evaporating dish. Evaporate to dryness very slowly on the steam bath. If the residue is golden, with no trace of pink, no borate is present.’ If it has a pink or rose tint, borate is present. The quantity may be estimated by comparison with standards prepared by evaporating to dryness Reagents very slowly known quantities of the borate solution, made up STANDARD BORATESOLUTION-(^) 0.16 gram of borax in 1 to a volume of 10 cc. with distilled water, to which 1 cc. of liter of distilled water (1 cc. contains 0.1 mg. BOs); (2) hydrochloric acid solution and 1 cc. of turmeric solution have 25 cc. of solution 1 diluted to 250 cc. (1 cc. contains 0.01 mg. been added. The standards may range from 0.000 to 0.50 mg. of BO,. Bod. TURMERIC SOLUTION-5grams of powdered turmeric which Standards containing 0.000, 0.0025, 0.0050, 0.0076, and 0.010 mg. of BOs show distinct differences in tint, and in samples 1 Received July 31, 1928. containing such quantities the BOa may be estimated to about 2 Published by permission of the Director, United States Geological 0.001 mg. Above 0.01 mg. the standards must have wider Survey. ranges-0.01, 0.03, 0.06, 0.10, 0.25, and 0.5 mg. of BO8 to a A m . Chem. J . , 9, 23 (1887).
ANALYTICAL EDITIOhT
28
show distinct gradations in color. With these larger quantities of BOs it may be advisable to use 0.5 cc. of turmeric solution instead of 1 cc., provided, of course, the same quantity is added t o both sample and standard. If the sample is high in dissolved mineral matter, the accumulation of salts in the bottom of the dish may make difficult a comparison with standards prepared from distilled water. With these samples small quantities of the salt solution, the quantity depending upon the mineral content of the samples, may be added to the standards t o make them more nearly comparable with the samples. It is difficult, however, t o obtain a similar deposition of salts in both sample and standards. If the accumulation of salts is too great for comparison with the ordinary standards, it may be better,to use a smaller volume of the sample, diluted to 10 cc., for the determination, rather than to try to duplicate the salt deposition. If the borate content of the sample is very low, it is sometimes advisable to use 25 cc. as the volume for both sample
Vol. 1, No. 1
and standard. It is necessary to evaporate the whole amount of each down a t once, rather than to evaporate a larger volume of t,he sample down in portions for comparison with standards prepared from a volume of 10 cc. Xatural waters may dissolve appreciable quantities of boron from the glass bottles in which they are collected, especially if kept in the bottles some time before testing for borax. It is advisable, therefore, t o make the test for borax as soon as possible after collection of the Pamples unless the bottles are known t o be satisfactory in this respect. Blank tests for borax in distilled water which has stood for several days in the bottles to be used will indicate whether or not borax is given up by the bottles. The salt solution used t o make the residue upon evaporation of the standards more nearly comparable with the samples, if the samples are high in dissolved mineral matter, should also be checked from time to time for borax dissolved from the bottle. A fresh salt solution is preferable t o one that has been standing in the bottle for some time.
Dimethyl-Alpha-Naphthylamine for Determination of Nitrite Ion‘ Frederick G. Germuth DEPARTMENT OF P U B L I C
A
WORKS,
BUREAUOF
S A reagent for the detection and estimation of nitrites
existing in minute portions in waters of known composition as well as in those of questionable origin, a-naphthylamine in conjunction with sulfanilic acid has acquired a popularity in analytical circles that it has been successful in securely retaining over a long period.2 The instability of the coloration produced by this compound in the presence of the nitrite radical introduces a disadvantage that is obvious; any efforts directed toward the remedying or elimination of this drawback would, it was believed, justify the study and subsequent labor essential to the accomplishment of the end sought. During the course of experiments carried on by the author a t this laboratory, in which certain naphthalene substitution products, including a- and P-naphthylamine, were employed in methylation processes, it was observed that dimethyla-naphthylamine is capable of producing a more distinct coloration than a-naphthylamine, in solutions containing small quantities of nitrite ion, and in addition, the color so formed possesses the property of stability and permanence. Experimental work was immediately undertaken to learn to what extent the utilization of the alkyl derivative of anaphthylamine might find application as a chemical reagent in the determination of the soluble salts of nitrous acid. The procedure and results are herein presented. Quality and Purification of Materials
The compounds employed-namely, sulfanilic acid, anaphthylamine, acetic acid, sodium nitrite, and aluminum hydroxide-were of the highest purity obtainable. The sodium nitrite was prepared according to the method advocated by the American Public Health A~sociation,~ as were also the solutions. The aluminum hydroxide was prepared by precipitation; a solution of aluminum chloride, crystal-
* Received June 25, 1928. 2
(1925).
Ilosvay, Bull. SOC. chzm , 131 2, 388 (1889) “Standard Methods for Examination of Water and Sewage,” p. 18
STANDARDS,
BALTIXORE, MD.
lized and then acted upon by pyridine-free ammonium hydroxide, furnished a compound of high purity. Standard tests made for the detection of chloride, nitrite, and ammonium compounds gave negative results. Basic fuchsin (magenta) was used in preparing the permanent standards, while dimethyl-a-naphthylamine was employed in the production of the experimental permanent standards. The latter compound possesses a boiling point of 145-146” C. a t 12 mm., and is practically free of extraneous substances. Method
The modus operandi followed in the experimental work and preparation of essential reagent solutions is that endorsed by the American Public Health As~ociation.~Ten experimental solutions of sodium nitrite of various degrees of dilution were prepared and, after treatment with a-naphthylamine reagent, were permitted t o stand for 10 minutes before comparison with the standards of basic fuchsin was made. The Nessler tube containing each test sample was replaced in its position in rack, and then closely observed in an effort t o discern any fading or discoloration in its incipiency. Table I shows the results of this inspection. Table I-Effect
of T i m e on Coloration of Experimental Nitrite Solutions TIMEBEFORE TIMEBEFORE
SOLUTIONNO2 CHAXGE OCCURS SOLUTION NO8 CHANCE OCCURS Gram MMinules Gram Minutes
Ten additional solutions were now made up, using the same amount of sodium nitrite as in the previous tests. They were treated in precisely the same manner as the preceding solutions, except dimethyl-a-naphthylamine, CloH7N(CH3)2,was substituted for the substance first employed, to produce the coloration sought. The results attained convinced one that the methyl derivative of the naphthalene-
