Micro-tests

Acetyl chloride test (for primary and secondary amines). In a semi-micro test-tube (75 x 10 mm.) treat 0-5 ml. (or 0-5 g.) of the compound with acetyl chloride drop by drop. Note whether reaction occurs. If no solid separates, pour the contents of the tube into 3 ml. of water and neutralise the aqueous layer with solid sodium bicarbonate. Observe whether a product different from the original compound is produced. 

Mikro-probe, /. micro test micro sample, -schnellbestimmung, /. rapid microdetermination. 

Figure 4.43 Benchmarking of untreated and pre-treated Y-piece micro reactors to a commercial micro test-tube for the hydrolysis of p-nitrophenyl-/ -D-galactopyranoside. Y-piece micro reactor ( ) commercial micro test-tube ( ) pre-treated Y-piece microreactor (A) [26],...

Table I. Borg-Warner Micro-Testing Program,...

A micro-test for organically combined sulphur in plants consists 7 in exposing the material to bromine vapour for several hours in order to bring about oxidation. After removing excess of bromine by means of ammonia or by volatilisation, the sulphate is precipitated by calcium chloride, the crystalline precipitate being examined on the following day. 

A comparison of methods for holding small O rings for micro test has been made33 which also describes a novel device using metal fingers which proved very satisfactory. 

Morgans et al61 carried out comprehensive trials to compare the IRHD and Shore micro tests concluding that the IRHD was better for very small test pieces but the Shore better for bent test pieces. They also note the fact that the Shore test is not totally non-destructive. This work was continued to include the normal IRHD and Shore A scales and to consider curved surfaces62. The results are a good illustration of the differences in measured hardness that can be found between different instruments with variation of test piece geometry. 

Adropof an acetonic solution of RDX or a small amt of the solid is evaporated with one drop of coned HC1 in a micro test tube. After cooling, a drop of Nessler soln is added. A positive test is indicated by the appearance of a brown or yellow ppt or turbidity (Ref 2, p 489)... 

Tetryl or Picrylnitromethylamine(pp 488-89) can be detected by treating(in a micro test tube) a drop of benzenic soln of the sample with powdered manganous sulfate filling the tube to 2/3 of its capacity. After evapg benzene, the tube is immersed (after covering its mouth with a disk of filter paper moistened with Nessler soln) into a bath preheated to 140° and the temp is raised to 150°. A gray or black Stain on the paper appearing within 5 mins indicates the presence of a nitramine, such as tetryl. 

Identification Place a drop of a saturated solution of sample into a micro test tube, and add a drop of a 0.5% solution of ammonium chloride and several milligrams of zinc powder. Cover the mouth of the tube with a disk of filter paper moistened with a solution of 5% p-dimethylaminobenzaldehyde and 20% trichloroacetic acid in hexane. Heat with a small flame for about 1 min. A pink to red-violet stain appears on the paper. 

Traces of turbidity and of colour are also readily distinguished in micro test-tubes (50 x 8 mm) or in micro centrifuge tubes. As a general rule, these vessels are employed in testing dilute solutions so as to obtain a sufficient depth of colour. The liquid in a micro centrifuge tube or in a test-tube may be warmed in a special stand immersed in a water bath (compare Figs. 11.22-23) or in the apparatus depicted in Fig. 11.47. The latter is constructed of thin aluminium or... 

Another method involves the use of an Emlch filter stick fitted through a rubber stopper into a thick-walled suction tube the filtrate is collected in a micro test-tube (Fig. 11.51). The filter stick has a small pad of purified asbestos above the constriction. 

Gas reactions may be performed in specially devised apparatus. Thus in testing for carbonates, sulphides, etc., it is required to absorb the gas liberated in a drop of water or reagent solution. The apparatus is shown in Fig. 11.53, and consists of a micro test-tube of about 1 ml capacity, which can be closed with a small ground glass stopper fused to a glass knob. The reagent and test solution or test solid are placed in the bottom of the tube, and a drop of the reagent for... 

Place 1 ml of the neutral or faintly alkaline solution in a micro test-tube, introduce a few small crystals of potassium cyanide, and then 2 drops of the reagent. Shake for 30 seconds. The green colour of the reagent changes to red. 

Thiourea (10%) intense yellow complex with bismuth(III) ions in the presence of dilute nitric acid. The test may be carried out on drop-reaction paper, on a spot plate, or in a micro test-tube. 

Place a drop of the test solution, which has been neutralized and then acidified with acetic acid in a micro test-tube and add a drop of the reagent. A yellow-green precipitate or opalescence (according to the amount of copper present) is obtained. 

For minute quantities of arsenic, it is convenient to use the apparatus depicted in Fig. 11.56. Mix a drop of the test solution with a few grains of zinc and a few drops of dilute sulphuric acid in the micro test-tube. Insert the funnel with a flat rim, and place a small piece of drop-reaction paper moistened with 20 per cent silver nitrate solution on the flat surface. A grey stain will be obtained. 

Place 0-2 ml test solution containing tin(II) ions (this may consist of the solution obtained from the Group IIB precipitate, reduced with magnesium) in a micro test-tube, acidify (if necessary) with dilute hydrochloric acid, add 0-2 ml 01m iron(III) chloride solution, followed by 0-3 ml 5 per cent tartaric acid solution (to prevent the formation of iron(III) hydroxide), 3 drops dimethylglyoxime reagent, and about 0 5 ml 2m ammonia solution. A red colouration is produced. 

Alternatively, treat a little of the test solution in a micro test-tube with a few drops of the reagent. A violet (purple) colouration is produced. 

Place a drop of the test solution or a little of the solid in the micro test-tube, and add a drop of 2m sodium hydroxide solution. Fix a small piece of red litmus paper on the glass hook and insert the stopper into position. Warm to 40°C for 5 minutes. The paper assumes a blue colour. 

Mix a few drops of the test solution with a little dilute sulphuric acid in a micro test-tube and tie (or otherwise fix) a piece of drop-reaction paper which has been moistened with a mixture of equal parts of the copper acetate and benzidine reagents to the top of the tube. A blue colouration is produced. 

Render the test solution almost neutral to bromothymol blue by treating it with dilute acid or alkali (as necessary) until the indicator turns green. Place a few drops of the test solution in a micro test-tube, and add a few drops of the reagent solution. A yellow colouration is obtained in the presence of a borate. It is advisable to carry out a blank test with distilled water simultaneously. 

Place a few milligrams of the test sample (or, alternatively, use the residue obtained by evaporating 2 drops of the test solution to dryness) in a micro test-tube, add a little pure diphenylamine and melt over a free flame. When cold, take up the melt in a drop or two of alcohol when the latter will be coloured blue. Sensitivity 5 pg (COOH)2. Concentration limit 1 in 10,000. 

In the presence of anions which are precipitated by calcium chloride solution, proceed as follows. Precipitate the acetic acid test solution with calcium chloride solution, and collect the precipitate on a filter or in a centrifuge tube. Remove the water from the precipitate either by drying or by washing with alcohol and ether. Mix a small amount of the precipitate with diphenylamine in a dry micro test-tube, add a little concentrated phosphoric acid, and heat gently over a free flame. Calcium phosphate and free oxalic acid are formed, and the latter condenses with the diphenylamine to aniline blue and colours the hot phosphoric acid blue. The colour disappears on cooling. Dissolve the melt in alcohol, when a blue colouration appears. Pour the alcoholic solution into water thus precipitating the excess of diphenylamine, which is coloured light blue by the adsorption of the dyestuff. The dye may be extracted from aqueous solution by ether. 

Place a drop of the neutral or alkaline test solution in a micro test-tube, and add 1 drop of m sodium chloride solution and 2 drops of the iron(III) periodate reagent. Carry out a blank test with a drop of distilled water simultaneously. Immerse both tubes for 15-20 seconds in water at 40-50°C. A white (or yellowish-white) precipitate indicates the presence of lithium the blank remains clear. 

In actual experiments, graduated micro(test)tubes (I (X) mm high with an inner diameter of 3 mm) were used. The total volume, 1.00 ml, of these tubes is divided into 100 graduations, and the sedimentation volume was read (or estimated) to... 

To 0.5 ml of urine in a micro test-tube add 100 Lil of 2M sodium hydroxide, and 100 li1 of chloroform, mix for 30 seconds, centrifuge in a high-speed centrifuge for 2 minutes, and inject 3 to 5 Lil of the chloroform extract on to both columns. Identify any peaks which appear by reference to the retention data listed in Table 17. Furdier systems and data for the gas Chromatography of narcotic analgesics are given on p. 198. 

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