FIELD and LABORATORY MICROANALYSIS by MEANS of a PORTABLE DROP REACTION KIT PHILIP W. WEST'
AND
LOTHROP SMITH
State University of Iowa, Iowa City. Iowa
M
UCH of the published material on qualitative analysis is chiefly of academic interest, and procedures for field tests and practical applications i n general are often confined to the blowpipe methods of the mineralogists, or to a few specific tests suitable only under certain conditions. The interest of the authors in compact and portable equipment for general qualitative analysis has led to the development of a kit utilizing modem drop reactions
and microchemical technics. Since this kit has proved quite satisfactory in practice, and permits the application of adequate tests for rather a large number of constituents, a description is offered in the hope that it may be of general interest. The entire kit is contained in a fishing tackle box, six by nine by fourteen inches, weighs nine pounds, comprises sixty-four reagents, and allows tests for thirtyeight constituents. Space for eight extra bottles is available in the kit as designed, allowing additional reagents to be added if desired. APPARATUS
The apparatus consists of a thick concave slide (used as a mortar), small pestle, thin concave slide (placed on colored paper and used as spot plate), colored paper, cigarette lighter (used as burner), microscope slide, 1
filter pipet (tapered capillaries with large end approximately 2 mm. in diameter), transfer pipets (capillaries approximately 1.0 mm. in diameter), platinum loop,
f,ner mFr
hand lens, centimeter rule, two watch glasses (micro preferred), cobalt glass, filter paper, razor blade, blowpipe for fusions, dissecting needle, chloride apparatus, Gutzeit apparatus. REAGENTS
These are contained in 10-ml. vials equipped with screw caps carrying applicator rods. Small calendar numbers, cut out with a cork borer, and protected by similar disc of "scotch tape," are stuck on the caps for identification. The reagents chosen have been selected for their stability, availability, and definite reactions. DETAILS OF TECHNIC
Preparation of sample: In the analysis of minerals
Department of Hygiene and Preventive Medicine.
139
or other substances not readily soluble in water or dilute hydrochloric acid, a sodium carbonate fusion is used, the details of which are as follows. Sodium Carbonate Fusion.-Prepare a carbonate bead in the loop of a clean platinum wire. Touch the warm (or moistened) bead to some of the finely powdered unknown and fuse. When the material is homogeneous, introduce a little sodium peroxide into the melt. Place the bead in a casserole and leach with distilled water. Decant the supernatant liquid into a test-tube and label as "Aqueous Group." Add a drop or two of dilute hydrochloric acid to the residue in the casserole and, after solution is complete, rinse into a second test-tube with a little distilled water. Label this portion the "Acid Group." Sodium Carbonate Separation.-Materials which are soluble in water or dilute HC1 may be divided into two groups by adding a little sodium peroxide plus a little sodium carbonate to the solution and filtering by means of a filter pipet. The filter plug with the precipitate is then placed in the tube used for the acid group, and solution completed by addition of a few drops of dilute HCl plus a little water. The filtrate should be blown out into the tube used for the aqueous g~oup. The sodium carbonate separatiun and thc fusion proccdwe both divide the clcments into the two folloiving groups. Aqueous Group Aluminum, antimony, arsenic, beryllium, boron, chloride, chromium, fluorine, iodine, molybdenum, phosphorus, potassium, selenium, silicon, sodium, sulfur, tin, tungsten, and vanadium.
Acid Group Barium, bismuth, cadmium, calcium, cobalt, copper, gold, iron, lead, magnesium, manganese, mercury, nickel, silver, strontium, titanium, uranium, zinc, and zirconium. Some elements such as aluminufn, antimony, arsenic, beryllium, uranium, manganese, and zirconium may be found in both groups. Sodium, arsenic, mercury, and chloride should be run on the oripinal sample. Before starting the actual anilysis the-solutions of both groups shodd be made acid and boiled to decompose the remaining hydrogen peroxide. They should then be made neutral or faintly acid to litmus. Fi1terina.-Filtration is carried out by placinp a ball of moist filter paper in the bell of a fil& pipet &f sucking the liquid up into the body of the pipet. The filter paper is then removed and the filtrate blown into the receivine vessel. If the filtrate is to be tested on filter paper a simple procedure is to allow the solution and precipitate to be drawn into a capillary tube, the end of the capillary placed firmly against a piece of filter paper held on a smooth surface, and the liquid allowed to diffuse out into the paper. The precipitate, which will remain a t the center of the spot, will not interfere with subsequent tests. General Hints.-In preparing the material for solution it is well to remember that HC1 gives insoluble
-
precipitates with Agt, Hgt, P b t t, T l t , C u t , Aut, S b + + + + + ,and B i t + + , alkaline silicates are broken down to SiOz, and insoluble oxides of arsenic, tellurium, tungsten, titanium, and molybdenum are formed. Any insoluble material should be filtered off,fused, and taken into solution by whatever means might apply. Observation of the preliminary treatment may give a good idea of the composition of unknowns. For example, the formation of a precipitate upon addition of HCl indicates that one of the substances mentioned above is present. A pink or yellow color upon addition of HC1 indicates the presence of titanium or vanadium (resulting from the reaction of these elements with hydrogen peroxide which is formed when sodium peroxide is treated with acid). The spot plate (a slide of the type used for hanging drop technic in bacterial work) used in this kit lends itself readily to various phases of the technic. It may be held over colored backgrounds as an aid in observing precipitates, and will also stand gentle heat in cases where the reactions must be hastened by heating. Care of the apparatus consists essentially of using only fresh capillary tubes each time, and washing and drying the casseroles, spot plates, and so forth, after each test. As a general rule in applying the tests, it is well to keep in mind that small drops used consistently will give as good results as large drops. The strength of the solution of the unknown need never be over 0.5 per cent. Stannous chloride, bromine water, concentrated HCl, HBOa, and NaOH attack the vial caps and therefore should not be left in the vials foi'more than a few days before being reblaced. I n the description of the tests which follow, the elements are placed in alphabetical order in their respective groups. This is to facilitate locating specific procedures when testing for random elements.
(1) Acetic acid (2 N). (2) Alizarin: To a saturated solution of alizarin in alcohol add HCl until yellow. Dilute with an equal amount of alcohol and filter. Alizarin S, (One per cent.) f4, Ammonia ~,~ ~-, - - ~~ ~(5) Ammonium (5 N). (6) Ammonium chloride (saturated). (7) Ammonium mercury thiacyanate: 9 g. (NH4)CNS and 8 g. HgClz dissolved in 100 ml. of water. (8) Ammoniummolybdate: Add35ml. of HNOa (sp. gr. 1.2) t o 100 ml. of a five per cent. solution of (NH,).Mo04. (9) Ammonium ~ersulfate(solid). (10j Ammonium phosphate ((NH&HPO~)(5 N). (I1) Ammonium sulfide (12) Aniline: Saturated solution of aniline hydrachloride in concentrated HCI. (13) ~ ~chloride r (N).i ~ ~ (14) Benzidine: Dissolve 0.05 g. benzidine in 10 ml. glacial acetic acid. Dilute to 100 ml. with water. (15) Bromine water. (16) Codeine sulfate (three per cent.). (17) copper (0.02 per cent.). (18) Dihydroxytartaric osazone (solid). ~~
~~
(19) . . Dimethyl-amino-benzal rhodanine: 0.03 per cent. in acetone. (20) Dimethylglyoxime: One per cent. in alcohol. (21) (Make up fresh.) One per cent. ~ - - ,Diohenvlcarbazide: . in alcohol. (22) Diphenylcarbazide thiocyanate: (Make up fresh.) To a saturated alcohol solution of diphenyl carbazide, add potassium thiocyanate crystals to saturation. (23) Diphenyl thimarbazane (dithizan): 0.002 per cent. in carbon tetrachloride. This reagent sttacks ordinary glass and so should be kept in Pyrex. (24) Hydrochloric acid (concentrated). (25) Hydrochloric acid (0.1 N). (26) Hydrogen peroxide (twenty Per cent.). (27) Magnesium powder. (28) Mercuric chloride (saturated). (29) Mercuric nitrate: ten per cent. mercuric nitrate in one per cent. nitric acid. (30) Nitric acid (N). (31) a-Nitroso-@-naphthol: Dissolve 2 g. a-nitroso-8-naphtho1 in 1W ml. ~lacial acetic acid and dilute with 100 . ml. water. (32) Oxalic acid (2 N). (33) Phosphomolyhdic acid (five per cent.). (34) Phosphoric acid (concentrated). (35) Potassium chromate (N). (36) Potassium chromate: one per cent. in normal acetic acid. (37) Potassium cyanide (5 N). (38) Potassium dichromate (solid). (39) Potassium ferrocyanide (2 N ) . (40) Potassium iodide ( N ) . (41) Potassium nitrite ( N ) . (42) Potassium thimyanate (2 N ) . (43) Potassium thiocyanate (solid). (44) Qninalizarin (saturated in alcohol). (45) Silver nitrate (solid). (46) Sodium acetate (saturated). (47) Sodium carbonate (anhydrous). (48) Sodium cobaltiuitrite (solid). (49) Sodinm hydroxide (5 N). (50) Sodium hydroxide (N110). (51) Sodium peroxide (solid). (52) Sodium phosphate (NaxHP03 (2 N ) . (53) Sodinm rhodizonate (make up fresh) (five per cent.). (54) Sodium thiosulfate ( N ) . (55) Stannous chloride: Normal in cpncentrated HCI. (56) Starch (solid). (57) Sulfuric acid (concentrated). e (58) Thiourea (ten per cent.). (59) Titan Yellow (0.1 per cent.). (60) Turmeric: Extract 20 g. turmeric with 50 ml. alcohol, filter, and dilute to 100 ml. with water. (61) Zinc (arsenic free). (62) Zinc sulfate (2 ~.-, . M. . (63) Zinc uranyl acetate. (64) Zirconium-alizarin lake: Add equal volumes of 0.17 per cent. alizarin S. t o 0.87 per cent. zirconium nitrate and dilute with five volumes of water.
tian of the sample. Some such as Mo, Cr, and V, which are not, may be removed by boiling with 1 drop of BaCIS: the excess Ba must then be removed with NaOH, evaporating to dryness, taking up in 2 drops of 8 0 and hltering. LI = 0.6 microgram LC = 1:77.000
.
Antimony Filter paper
(A) Watch glass: 1 drop of soh- Blue tion, 1 drop of ammonium sulfide, remove excess liquid, 1 drop of HC1 (couc.). (B) Filter paper: 1 drop of phosnbomolvbdic acid, 1 drop of solution {A), hold in steam. Note: The above treatment of the sulfide precipitate gives the antimony as SbCll and any tin as SnCL. Under such conditions, the test is specific for antimony. If tin is known t o be ahsent, proceed from (B). The color formation is slow, but is hastened by the steaming. LI = 0.2 microgram LC = 1:250.000
Gutzeit apparatus
Place a few grains zinc, 1 ml. HCI Yellow(N/10), 4 drops of SnClr in the appa- brown ratus. Add a few drops of test solution and close the apparatus with assembled stopper. Note: This test is specific. The stopper is assembled by placing PbAc paper in the body of the tube (to remove any H 8 ) and planing HgCh paper over the top of 'the tube. Instead of using lead acetate paper, it is often advantageous to place a loose plug of cotton saturated with Cu.Cln in the body of the t u b e t h e Cu2Cb will remove PHI and SbHa as well as H*S. .. .. LI = 1microgram LC = 1:40.000
Casserole
1 drop of solution, 1 drop of HCI Blue (NllO), evaporate to dryness and bake to expel N H 4 +salts. Dissolvein 1 drop of NaOH (NIlOX add 2 drops quinalizarin. Notes: Run blank. NHaf interference is prevented by its decomposition. Interference from iron and magnesium does not occur in this procedure because of their separation during the preparation of the sample. LI = 0.15 microgram LC = 1:353.000
Casserole
1 drop of turmeric, 1drop of salution. Green 1 drop of HCL (N/10), evaporate t o dryness, 1 drop of NaOH (5 N ) . Notes: Some other compounds give a stain (reddish brown) with this reagent, but their color is not changed
Arrenic
Beryllium
~
ANALYTICAL PROCEDURES APPARATUS
PROCEDURE WITH EXPLANATORY NOTES COLOR
*gwousonow
Spot plate
Aluminum 1 drop of solution, 1 drop of NaOH Pink (N/10), 1 drop of alizarin S., 2 drops acetic acid. Note: Most interfering substances are precipitated during the prepara-
Boron
Phosphorus
t o green by the NaOH treatment. Oxidizine aeents such a s nitrites. chromates, and so forth, must be decomposed before applying this test. LI = 0.02 microgram LC = 1:2.500,000
- -
special apparatus
Casserole
Chloride A few grains of the solid substance Purple are mixed with powdered potassium dichromate and placed in the ignition tube of the chloride apparatus. A drop of Hi301 (canc.) is added, and the charged reaction capillary put in place. Heating the ignition tube will color the reagent in the capillary purple. The reaction capillary is charged by touching its tip t o a drop of freshly prepared diphenylcarbazide. Note: This test may be madein the presence of iodine and bromine if a little phenol is added t o the ignition tube. Gives no test with insoluble chlorides (AgCI). LI = 1.5 micrograms LC = 1:33.000 Chromium
Spot plate
Spot plate
Spot plate
One drop of solution, acidify (HzSOJ. 1 drop of diphenylcarbazide. Note: Molybdenum and vanadium interference may be inhibited with oxalic acid. LI = 0.5 microgram LC = 1:100,000
Spot plate Violet
Fluoridc One drop of solution, 1 drop of HCI Fades from (conc.), 1 drop of HnSOl (conc.), 1 pink to drop of zirconium-alizarin solution. yellow Allow to stand five minutes. Run blank. Suter: Phosphates, arscnates and oxnlatcs intrrfcre. Interference from oxnlatcs may bc prevented b y roasting the sample prior to testing. LI = 2 micrograms C LC = 1:250,000 Iodine One drop of solution, 1 drop of HCI Blue (N/10), 1drop of fresh starch paste, 1 drop of KNO2. Notes: Specific. LI = 2.5 micrograms LC = 1:20,000 Molybdcnlrm
Filter paper
One drop of HCI (conc.), 1 drop of 'Red
(edge solution (on acid spot), 1 drop KCNS, of spot) 1 drop of SnCL. Note: Both molybdenum and tungsten react with KCNS in the presence of SnCl. and HCI. The molybdenum gives a red color soluble in the HCI (therefore the red is a t the edge of the drop): the tungsten reacts t o give a blue, insoluble ppt. (remains in the center of the drop). LI = 0.1 microgram LC = 1 :25,000
Two drops of ammonium molybdate. Blue 1drop of solution, 1 drop of benzidine, 3-6 drops of Na acetate. Notes: Soluble silicates and phosphates both react with ammonium molybdate in nitric acid solution to form complex molybdates. When these complex molybdates are treated with benzidiue, they are reduced t o molybdenum blue, and simultaneously the benzidine is oxidized t o a blue quinoid compound. Phosphates react to form the molybdates in the cold, while the silicates require gentle heating before they undergo the reaction. If silicates are present, they may be removed by converting to insoluble silica by twice evaporating the test portion to dryness in the presence of HCL. The residue may then be leached with dilute HNOn and the test applied. LI = 0.05 microgram LC = 1 : 1,000,000 Potassium One drop of solution, 1 drop of acetic Yellow add, a few grains of sodium cobaltini- ppt. trite. Heat gently. Notes: Thallium and lithium yield precipitates which cannot be distinguished from the potassium test; therefore, in the presence of these dements, the eobaltiuitrite test cannot be used. The next best test is the violet h m e shown by potassium compounds when viewed through cobalt glass. .. 1.1 = 4 micrograms LC = 1:12.500 Selenium
Casserole
One drop of solution, 5 drops of sulfuric Blue acid (cauc.), digest. until colorless (cover casserole to preven.t excessive evaporation), cool, add 1 drop of codeine sulfate. Notes: Vanadium is the only interfering substance. LI = 0.08 microgram LC = 1:8,000.000
Casserole
Two drops of ammonium molybdate, 1 drop of solution, warm, cool, 2 drops of oxalic acid, 1 drop of benzidine, 3-8 drops of sodium acetate. Notes: See notes on phosphorus. To detect silicon when phosphate is present add 1 drop of solution to two drops of reagent, warm, filter off the precipitate of ammonium pbosphomolybdate, cool the filtrate and proceed as before. LI = 1 microgram SiOz LC = 1:50,000 I n presence of phosphate ~1 = 6 micrograms SiOl (in presence of up to 250 parts PpOr) LC = 1:8300
Siliccin Blue
Sodium Spot plate
ACID GROUP
(A) Watch glass: 2 drops of solu- Yellow tion, 1 drop of ammonium sulfide, 1 drop of (NH&COs, filter. (B) Spot plate: Place filtrate from "A" on a spot plate, neutralize with acetic acid; 6 8 drops of zinc uranyl acetate. Notes: The treatment with ammonium sulfide removes all interfering elements, thus making the test specific. LI = 12.5 micrograms LC = 1:4000
.
Barium Filter paper
Sulfur Casserole
One drop of solution, 1 drop of Hg Yellow (NO&, evaporate nearly to dryness. 2 drops of water. Notes: The method of fusing substances in the presence of sodium peroxide in preparing them for solution oxidizes any sulfur compounds t o sulfate, which, when evaporated with the reagent and treated with a drop of water, forms a yellow basic mercuric sulfate. The test is specific. LI = 1.2 micrograms LC = Solution is evaporated t o neardryness.
Spot plate
Spot plate
Tin Filter paper
(A) Watch glass: 1 drop of solu- Blue tion, 1 drop of ammonium sulfide, absorb excess liquid, 1 drop of HCI (conc.), a few grains powdered magnesium. (B) 1 drop of solution from "A," 1 dron acid. . of nhomhomolybdic . . Notes: See notes under antimony. When the sulfide precipitate is dissolved in acid and reduced, any tin present reacts with phosphamolybdic acid to give a blue ~olor. The test is specific even in the presence of antimony. C LI = 0.03 microgram LC = 1:1,670.000
.
Spot plate (black)
Tungsten Filter paper
One drop of HCI (conc.), 1 drop of Blue solution in center of acid spot, 1drop of KCNS, 1 drop of SnC1,. Notes: See notes under molybdenum. LI = 4 micrograms LC = 1:12.500
Vanadium Filter paper
One drop of aniline, 1drop of HNO~,1 Green drop of solution. Notes: Chromates give similar stains, but may be reduced to chromium chloride, which does not react, by boiling with concentrated HCI. LI = 4 micrograms LC = 1:9000
Spot plate
One drop of solution. 1 drop of fresh Brown sodium rhodizouate, 1 drop of HCI (N/10). Nates: Bs, Sr, and P b all read with this reagent, but treatment of the stain with dilute HCI serves as a means of differentiation-with the HCI, the Sr stain disappears a t once. the Ba stain fades more slowly, and the P b stain turns purplish. Ba can thus be detected in the presence of Sr and Pb. 1.1 = 0.25 microgram LC = 1:200,000
Bismuth One drop of solution, 1 drop of thiourea, 1 drop of HNOs. Notes: Specific in absence of members of the aqueous group. LI = 0.5 microgram LC = 1:75,000 codrnium One drop of diphenylcarbazide thiocyanate, 1 drop of solution, 1 drop of NHdOH. Note: Co gives the same reaction; therefore in its presence the test is inconclusive. Interference from other elements is inhibited by the presence of NHIOH. Since the reagent is colored, a blank should be run. LI = 4 micrograms LC = 1:12,500 Calcit+p " (A) "Watch glass: 1 drop of solution, 1 drop of ammonium sulfide, warm, filter. (B) Spot plate: Blow out the filtrate from "A" on a spat plate, add a few grains dihydroxytartarjc osazone. Notes: Interfering substirnces are removed by the ( N H d d treatment. The reaction is slow, and fifteen minutes may be needed before a noticeable precipitate is obtained with small amounts of Ca. LI = 0.01 microgram LC = 1:5,000,000 -
Yellow
Violet
White precipitate
Cobalt (A) Watch glass: 1 drop of solu- Brown tion. 1 drop of NHXI, 2 drops of NH,OH, 2 drops of H1O. Filter. (B) Watch glass: Filtrate from "A," 2 drops of phosphoric acid, 1 drop of potassium iodide, 2 drops of sodium thiosulfate. (C) Spot plate: Filtrate from "B," 1 drop of n-nitroso-(-naphthol. Notes: If desired, greater sensitivity may be obtained by use of (nitroso-cr-naphthol. Most interfering substances are removed bv the ammonium hydroxide precipitation. The second precipitation with p o t a s sium iodide removes any interfering
144 copper as Cu&: free iodine, also in the reaction, is destroyed by the NasSnOl. Nickel also gives a brown color with this reagent, but it may be faded by a drop of dilute HC1. If iron, zirconium, vanadium, copper and nickel are known to be absent proceed from "C."
Copper Casserole
Filter paper
Spot plate
Spot plate
Casserole
One drop of solution, 1 drop of ( N H h Violet HP04,acidify (conc. H d 0 3 , l drop of ZnS04. 1 drop of ammonium mercuric thiocyanate, warm. Notes: Iron interference is inbibited by the phosphate. Cobalt and nickel interfere. LI = 0.1 microgram LC = 1 :5OO,OOO Gold One drop of solution, 1drop of SnCIs Purple 1drop of KCNS, boil in water. Notes: Mercury and selenium interfere, and in their presence the test is indetermiu+te. Molybdenum gives a stain similar to that of gold, but the color fades upon addition of potassium thiocyanate and boiling. LI = 3 micrograms LC = 1:10.000 Iron
One drop of solution, 1 drop of KCNS, ~ e d 1 drop of HCl (N110). Note: If arsenates, oxalates, tartrates, and so forth, are present they must be destroyed by roasting or by the fusion procedure. Molybdenum, fluoride, and phosphate do not interfere as they appear in the aqueous group. LI = 0.25 microgram LC = 1:200,000 Lead One drop of solution, 3 dro& of KCN, Pink 1 drop of NHICI, 1 drop of dithiion. Notes: Run blank, as the potassium cyanide imparts some color to the reagent. Dithizon gives a specific test for lead in the presence of potassium cyanide and ammonium chloride. The reagent should be a deep green color, and should be prepared fresh five or six times a year. I t is well t o keep a stock solution in a pyrex bottle and 6ll the vial only before taking the kit into the field. LI = 0.1 microgram LC = 1:1,000,000
Mercury Watch glass: 1 drop of solution, 1 Pink drop of hydrochloric acid (1 N), 4 drops of NarHP04, filter an filter paper, 1 drop of dimethyl-amino-henzal rhodamine on edge of spot. Notes: Any interference from silver or copper is prevented by their precipitation with the hydrochloric acid and sodium phosphate. Because of the color of the reagent, it is well to run a blank. LI = 1 microgram LC = 1:50.000 Nickel Watch glass: 1 drop of solution, 1 Pink .drop of hydrogen peroxide, 1 drop of ammonium carbonate, 1 drop of ammonia. Filter on paper, 1 drop of dimethylglyoxime on edge of spot, warm. Notes: Any interference due to iron, cobalt, or manganese is prevented by their removal wiih ammonium carbonate. LI = 1 microgram LC = 1:300,000 Silver Spot plate
A. Watch glass: I drop of solution, Red 1drop of ( N H W O s , filter. B. Spot plate: filtrate from "A," 1 d r m of KCrO'. 1 drop of acetic acid. Sores. .%ny interfering substances a r t imcipitart:cl h y the (SHACCh SO thnr the tesr is a~ecilic. If in a lahoratory, observe the test under a yellow light as greater sensitivity may be obtained. LI = 0.8 microgram LC = 1:40,000
Filter paper
one drop of solution, 1 drop of K r Brown
Magnesium Spot plate
(A) Watch glass: I drop of solution, Pink 1 drop of ammonium sulfide, warm, filter. (B) Spat plate: Filtrate from "A," 1 drop of titan yellow, 1 drop of NaOH
Notes: All interfering substances are removed by the ammonium snlfide. The sulfide separation may be omitted if iron, cobalt, cadmium, or nickel alone are present by adding a drop of potassium cyanide prior to the addition of the reagent and alkali. LI = 1.5 micrograms LC = 1:3300 Manganese One drop of solution, 1 4 drops of Violet AgNOo 1drop of HIPO,, a few grains ammonium persulfate, warm. Notes: Chloride, bromides, and so forth, do not interfere if sufficient silver nitrate is added t o insure a n excess over that required to precipitate the halogen. Under these conditions the reaction is specific. LI = 0.1 microgram LC = 1 : 500,000
Slrontium CrO* 1drop of sodium rhodizonate on edge of spot. Notes: See notes under barium. Tnterference from lead and barium is
Zirconium
prevented by their precipitation as the chromate. 1.1 = 3.9 micrograms (in presence of barium or lead) or 0.45 microgram (strontium alone) LC = 1 :12.800
Spot plate
One drop of solution, 1drop of HCI, 1 Brown drop of alizarin, heat gently.
to pink
Notes: Specific under test conditions. LI = 0.5 microgram LC = 1:100.000
Tilanitim Spot plate
One drop of solution, 1 drop of H8P04, Yellow 1 drop of H202. Notes: Molybdenum, vanadium, and chromium appear in the aqueous group and so do not interfere. Iron interference is prevented by the phosphoric acid. LI = 2 micrograms LC = 1:2500
Uranium Filter paper
Casserole
Watch glass: 1 drop of solution, four drops of Na&03. Filter on filter paper, one drop of potassium ferrocyanide on edge of spot. Note: The sodium thiosulfate reduces any iron and copper and precipitates any titanium as TiO.. There are no other substances which inter fere. LI = 4 micrograms LC = 1:12,500
Brown
Zinc One drop of solution, 1drop of ( N H d r violet HPO,, 2 drops of HBSO,,1drop of CuSO,, 1 drop of ammonium mercuric thiocyanate, warm. Notes: See notes for copper. Large amounts of copper interfere and should be removed by precipitation with KI. The free iodine set free should be destroyed by a d d i i a drop of Nadn08. LI = 0.2 microgram , LC = 1:250,000
Fero~.F., "Qualitative Anslyse mit Hilfe von Tupfelreaktionen," 2nd ed., Akademische Verlagsgesellschaft M. B. H., Leipzig, 1935. FEIGEL,F.. "Spot tests," Nordeman Publishing Co., New Yark City, 1937.
DISCUSSION The convenience ,and compactness of the equipment described, combined with its wide applicability, will suggest numerous uses to its possessor. Each individual will undoubtedly wish to introduce variations in content and procedure to suit his particular needs. While the tests used are given in the majority of cases either by Watson or by Feigl, they have been modified to conform with the two group separations obtained in the preparation of the sample for analysis. This preliminary separation removes many interfering substances and therefore must be made before applying the above tests. If additional confirmation of the presence of a given constituent is desired, it will be found in many cases that the reagents and apparatus included may be used, under slightly modified conditions, for detection of substances other than those for which they were included. Thus, diphenylthiocarbazoue may be used to confirm Cu, Zn, Hg, Au, and Ag; the flame test for Sr, Na, and K; HaOzfor V; Pb may be confirmed by either the sulfide or chromate tests; HCl and Zn may be used for W; quinalizarin will serve for Mg, and the . SiF4reaction for fluorine. .. ACKNOWLEDGMENT
The suggestions and aid of Dr. G. A. Abbott of the University of North Dakota during the initiation of this project are gratefully acknmledged.
TREADWELL and HALL."Analytical chemistry," John Wiley and Sons, Inc., New York City, 1937, Vol. I. WATSON, Min. Mac., 2 4 2 1 3 5 (1935).
