Sodium hydroxide spotting test

In this method the undyed fabric is spotted with 30% solution of caustic soda and then both mercerized and undyed spotted fabric samples are dyed by using Benzopurpurine. If the fabric is fully mercerized, the spots will not be evident after dyeing. On the other hand, if the fabric is not mercerized or semi-mercerized, dark spots will be evident and the degree of mercerization can be evaluated on comparing the spots. 

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Procedure. A small amount of the solid test material or a drop of its solution is treated in a micro test tube with several drops of chromic-sulfuric acid (preparation see Vol. II page 65). The open end of the test tube is covered with a disk of filter paper moistened with 2 N sodium hydroxide. The test tube is kept for 5 minutes in boiling water. The disk of reagent paper is then placed on a glass plate, spotted with several drops of permolybdic acid solution (for preparation see Vol. II page 68) and then dried with a current of cold air. If iodine is present, a brown fleck will appear but it fades within a few minutes. The stain is then treated with a drop of 0.1 % alcoholic solution of fluorescein. A positive response is indicated by the development of a red spot. 

Reduction to S(IV) is the basis of two spot tests of Feigl, although these apply to other S(VI) classes, e.g. sulphonamides. Thus Feigl and Lenzer fused the sample with alkali to yield sulphite, then treating with hydrochloric acid and warming to expel sulphur dioxide they detected the latter with nickel(II) hydroxide on test paper, which yielded ultimately the black Ni(IV) oxyhydrate (see also Section C). In the other test FeigF fused the sample with sodium formate/alkali, cooled and acidified with sulphuric acid to liberate sulphur dioxide in this case also. This was detected by a ferric chloride/potassium ferricyanide reagent which yielded a blue colour (Prussian, Turnbull s). 

The usual sugar-reagents do not serve to detect cyclitol spots (except those of inososes). Ammoniacal silver nitrate has been widely used, but the best results90 are obtained with separate solutions of silver nitrate in acetone and sodium hydroxide in ethanol.91 The Scherer test has been adapted for use on paper chromatograms,91 and other reagents are useful in certain instances.89-90... 

Sometimes it may be necessary to use the peptides solubilized and unbound to the cellulose membrane. If it is necessary to release the peptides from the membrane, one method is to expose the entire dry membrane overnight in a glass desiccator containing ammonia gas. The strong basic environment leads to a break of the ester bond to the cellulose by forming a C-terminal amide (see Note 8). The next day, punch out the spots and transfer the discs into wells of microtiter plates (MTPs) or into vials in which you can dissolve and test the released peptides (see Note 9). If a free carboxy terminal is desired on the peptides, then do not treat the membrane with ammonia gas, punch out the spots and expose them to a basic aqueous solution, for example, ammonium hydroxide or sodium hydroxide (26). 

Place a drop of the acid, neutral or ammoniacal test solution on a spot plate and mix it with 1 drop sodium hydroxide (2m) solution and 1 drop potassium cyanide (10 %) solution. Introduce 1 drop of the reagent and 2 drops formaldehyde solution (40%). A brown precipitate is formed, which very rapidly becomes greenish-blue. The reagent alone is red in alkaline solution and is coloured violet with formaldehyde, hence it is advisable to compare the colour produced in a blank test with pure water when searching for minute amounts of cadmium. 

Place a drop of the test solution (which has been treated with just sufficient of m sodium hydroxide solution to give the tetrahydroxaluminate ion [Al(OH)4]-) on a spot plate, add 1 drop of the reagent, then drops of acetic acid until the violet colour just disappears and 1 drop in excess. A red precipitate or colouration appears. 

The spot-test technique is as follows. Place a drop of the test solution on a spot plate and add 1-2 drops of the reagent. It is essential that the solution be strongly alkaline the addition of 1 drop of 2m sodium hydroxide may be advisable. According to the concentration of magnesium a blue precipitate is formed or the reddish-violent reagent assumes a blue colour. A comparative test on distilled water should be carried out. 

Place a drop of the test solution on a spot plate, introduce a drop of reagent and a drop of 2m sodium hydroxide. A red colour or precipitate is produced. 

Place a drop of the test solution and a drop of distilled water in adjacent cavities of a spot plate and add 2 drops of the reagent to each. If the solution is acid, it will be coloured yellowish-red by the reagent. Add 2m sodium hydroxide until the colour changes to violet and a further excess to increase the volume by 25 to 50 per cent. A blue precipitate or colouration appears. The blank test has a blue-violet colour. 

The spot-test technique is as follows. Mix a drop of the test solution with a drop of concentrated sodium hydroxide solution on a watch glass. Transfer a micro drop of the resulting solution or suspension to drop-reaction paper and add a drop of Nessler s reagent. A yellow or orange-red stain or ring is produced. 

The spot-test technique is carried out as follows. Place a drop of the test solution in the tube of Fig. 11.56, add 1-2 drops 20 per cent sodium hydroxide solution and a few milligrams of Devarda s alloy. Place a watch glass with a drop of p-nitrobenzene-diazonium chloride reagent (for preparation, see under Ammonium, Section III.38, reaction 8) on its underside upon the funnel stopper. Heat the apparatus gently for a short time. Add a tiny fragment of calcium oxide to the drop of the reagent a red ring forms within 10-15 seconds. 

To determine whether the coupling reaction is completed, a drop of the reaction mixture is placed on filter paper. The colorless ring surrounding the speck of dye is treated with a drop of a solution of a reactive coupler such as sodium -naphtholate, R salt, or resorcinol, and then with a drop of soda solution or dilute sodium hydroxide. If unused diazo compound is present, dye is formed in the test spot. If the dye being made is easily soluble so that no colorless ring is formed, a small portion of the reaction mixture is treated in a test tube with salt to precipitate the dye, and a drop of this mixture is then used for the test. The presence of unused coupler can be determined in a similar manner, using a diazo solution to test the colorless ring. 

A quick and simple test is to spot the sample with 27 to 30 per cent sodium hydroxide solution and then to dye it with benzopurpurine. If it has not been mercerized a deeper colour will appear where the spots were, but this will not be the case with mercerized cotton. 

Place a drop of the acid, neutral or ammoniacal test solution on a spot plate and mix it with 1 drop sodium hydroxide (2m) solution and 1 drop potassium cyanide (10%) solution. Introduce 1 drop of the reagent and... 

Sodium Salt. The crude salt is dissolved in methanol, using 100 ml. of solvent for each 60 g. of product. A 5 per cent solution of sodium hydroxide in methanol is added in just sufficient amount to render the solution permanently alkaline, as indicated by spot tests with phenolphthalein. Since difficulty may be experienced in filtering the basic solution, it is recommended that impurities be separated from the alcoholic solution by centrifugation. The solvent is removed by concentration and crystallization under reduced pressure to yield a product consisting of the monohydrate, which on drying over sulfuric acid is converted into the anhydrous salt. Yield of purified product from... 

Phenylhydrazine Cacotheline in sodium hydroxide solution Treat test solution with reagent on a spot plate Blue product 0.02... 

Sokolowska [63, 64] detected and determined tritolyl phosphate in PVC by extracting the additive with diethyl ether for 16 hours, the solvent was evaporated off, and a solution of the residue in chloroform was applied to layers of Silica gel G. Chromatograms were developed with benzene - ethyl acetate (20 1) and the spots of tritolyl phosphate were located with 0.5 N ethanolic - potassium hydroxide and diazotised 4-nitroaniline solution. The contents of total phenols and o- and p-cresols were determined by mixing the test solution (20 ml) containing 0.25 to 2 mg of phenols per litre, with diazotised 4-nitroaniline solution (5 ml). Borate buffer solution (28.42 g of Na2B40y IOH2O and 13 g of sodium hydroxide per litre (20 ml) was added and these solutions were then diluted to 50 ml with water and after 15 to 30 minutes, the extinction was measured at 485 nm against a... 

Pataki [121] has detected creatinine in urine on cellulose-D-layers. This procedure enables the creatinine to be separated from other JafF6-chromogens which interfere in the colour reactions on which many methods of determination are based. Quantitative evaluation of the creatinine spots, obtained using picric acid/sodium hydroxide, is possible since there is a linear relation between the square root of the spot surface area and the logarithm of the amount of substance applied (see p. 136) [122]. The rehabihty of the creatinine determination has been tested by parallel determinations of various amounts of creatinine in standard solutions and in urine. Tests on recovery gave a value of 95.7 3.4% of the creatinine added. Up to 20 (xg creatinine or ca. 20 [xl urine can be used in one determination larger amounts can lead to overloading of the layer. 

Procedure. A small amount of the solid sample or a drop of the test solution is placed in a micro test tube or in a depression of a spot plate and made slightly alkaline, if necessary, by adding a drop of sodium hydroxide solution. One or two drops of the reagent solution are added to the mixture. A positive response is indicated by the production of a black precipitate (HgS) immediately or after a short interval. 

Procedure. A drop of the test solution is stirred on a spot plate with a drop of a saturated solution of lead chloride, a drop of 2 JV sodium hydroxide, a drop of 6 % potassium cyanide, and finally 2 drops of stannite solution. According to the bismuth content, a brown to black coloration appears either immediately or after a few minutes. 

Procedure. A drop of the acid, neutral, or ammoniacal test solution is mixed on a spot plate with a drop of 10 % sodium hydroxide and one of 10 % potassium cyanide. Then a drop of the reagent and two drops of 40 % formaldehyde are added, with stirring. In the presence of cadmium, a blue-green precipitate or coloration is formed. The reagent itself is red in alkaline solution and is colored violet by formaldehyde. Hence, with small amounts of cadmium, the color should be compared with that of a blank test. 

Procedure, The test is conducted in a depression of a spot plate or on filter paper (S S No. 601). One drop of the neutral or weakly acid test solution is treated with a drop of freshly prepared 0.2 % sodium rhodizonate solution and one drop of 0.6 iST sodium hydroxide. The solution is mixed by blowing briefly... 

Procedure. A drop of the test solution and of phosphomolybdic acid solution are mixed on a spot plate, and a drop of 40 % sodium hydroxide solution is added. According to the cerium content, a more or less intense blue color or precipitate appears. 

Procedure. A spot plate or micro crucible is used. A drop of the neutral or acid test solution is treated with a drop of the reagent and then made alkaline with 1 N sodium hydroxide. If the color changes from red-violet to cornflower-blue, copper is present. When very small quantities of copper are involved, a mixed color appears. In this case, it is best to use not more than a microdrop of the reagent and to compare the color with that obtained from a solution known to contain no copper. 

Filter paper impregnated with the reagent solution may also be used. A drop of the neutral or extremely weak acid test solution is allowed to soak into the paper, and then is spotted with a drop of 1 N sodium hydroxide. A blue fleck or ring, depending on the copper content, appears on the red-violet reagent paper. The reagent paper is stable. 

Procedure. Dowex 1X1 (50-100 mesh) is treated with 20 times its volume of a 0.01 % solution of Xylidyl Blue I or II in ethanol. A drop of the test solution is mixed on a spot plate with one drop each of 0.5 iST sodium hydroxide, saturated aqueous glucose and 50% aqueous triethanolamine to make the pH 10-12. A few beads of the treated resin are then added. A purple color appears in the presence of magnesium. 

Procedure. The test is conducted on a spot plate. A drop of the test solution is treated with one drop each of a 1 % solution of 4-pyridylpyridinium dichloride in water, 1 N sodium hydroxide, and concentrated hydrochloric acid. It is imperative that this order be followed. If hydrazine or its salts are present, an orange to red color is formed. 

Procedure. Single drops of test solution, 1 N sodium hydroxide and 1 % nickel sulfate (hexahydrate) solution are placed in succession in a depression of a spot plate. A black or grey precipitate appears, according to the quantity of persulfate present. 

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