Stannous chloride method

In a further method [67] for the determination of ammonium lactate extractable (i.e. available) phosphorus in soils, the sample 5g is extracted with 100ml acidic ammonium lactate and then phosphate determined by flow-injection analysis using the stannous chloride method [68]. 

Tecator Ltd., Sweden. (1983) Application Note No. AN 60/83. Determination of Phosphate Stannous Chloride Method. 

They obtained the following results p-Dinitrostilbene, reduced in alkaline solution, gives p-azoxystilbene in hydrochloric-acid solution with addition of stannous chloride (method of C. F. Boehringer Sohne), p-diaminostilbene. 

POi, analyzed by the Stannous chloride method (Standard Methods, APHA, 1980). 

Two methods for determining platinum are described here in detail the well-known insensitive stannous chloride method, and a sensitive method based on an ion-associate of Pt(II) with SnCb and Rhodamine 6G. ... 

Extraction of Pt(IV) with iV-n-octylaniline followed by the determination of the metal by the stannous chloride method has been investigated [1]. The 99.6-99.8% recoveries of Pt from electrical contact, solder and oakay alloys were reported. 

The stannous chloride method has been applied to the determination of platinum in Pt and Pt-Ru catalysts with carbon support by direct and derivative spectrophotometry [2]. The calculation of the first-derivative spectra allows the determination of Pt in the presence of Ru. 

CgH,N,Cl -h zSnCl, + 4HCI = CeHjNH NH, HCl + zSnCI when treated with an acid solution of stannous chloride (e.g., a solution in hydrochloric acid) but the yields are not as high as those obtained by the above sulphonate method. 

It is advisable to test a small portion of the filtrate for platinum by acidifying with hydrochloric acid and adding a few drops of stannous chloride solution a yellow or brown colour develops according to the quantity of platinum pVesent. The yellow colour is soluble in ether, thus rendering the t t more sensitive. If platinum is found, treat the filtrate with excess of formaldehyde and sodium iQrdroxide solution and heat,- platinum black septarates on standing and may be filtered and worked up with other platinum residues (see Method 3). 

Reduction of methyl orange to />-aminodimethylaniline. Method 1. Dissolve 2 0 g. of methyl orange in the minimum volume of hot water and to the hot solution add a solution of 8 g. of stannous chloride in 20 ml. of concentrated hydrochloric acid until decolourisation takes place gentle boiling may be necessary. Cool the resulting solution in ice a crystalline precipitate consisting of sulphanilic acid and some p-aminodimethylaniline hydrochloride separates out. In order to separate the free base, add 10 per cent, sodium hydroxide solution until the precipitate of tin hydroxide redisaolves. Extract the cold solution with three or four 20 ml. portions of ether, dry the extract... 

It may also be prepared by the reduction of phenyldiazonium chloride with the calculated amount of a solution of stannous chloride in hydrochloric acid, but the yield is not so high as that obtained by the above sulphite method ... 

Recovery of the wopropyl alcohol. It is not usually economical to recover the isopropyl alcohol because of its lo v cost. However, if the alcohol is to be recovered, great care must be exercised particularly if it has been allowed to stand for several days peroxides are readily formed in the impure acetone - isopropyl alcohol mixtures. Test first for peroxides by adding 0-6 ml. of the isopropyl alcohol to 1 ml. of 10 per cent, potassium iodide solution acidified with 0-6 ml. of dilute (1 5) hydrochloric acid and mixed with a few drops of starch solution if a blue (or blue-black) coloration appears in one minute, the test is positive. One convenient method of removing the peroxides is to reflux each one litre of recovered isopropyl alcohol with 10-15 g. of solid stannous chloride for half an hour. Test for peroxides with a portion of the cooled solution if iodine is liberated, add further 5 g. portions of stannous chloride followed by refluxing for half-hour periods until the test is negative. Then add about 200 g. of quicklime, reflux for 4 hours, and distil (Fig. II, 47, 2) discard the first portion of the distillate until the test for acetone is negative (Crotyl Alcohol, Note 1). Peroxides generally redevelop in tliis purified isopropyl alcohol in several days. 

A cousin to this reduction is one using stannous chloride (a.k.a. SnCb, a.k.a. Tin chloride) which is done exactly as the calcium one except that about lOOg of SnCb is used in place of the Mg or Ca and the addition occurs at room temperature and the solution is stirred for one hour rather than 15 minutes. Some very good reductions that operate almost exclusively at room temperature with no pressure and give almost 100% yields are to follow. The only reason Strike did not detail these methods is that some of the chemicals involved are a little less common than Strike is used to but all are available to the public. These alternatives include acetlylacetone and triethylamine [73], propanedithlol and trieth-ylamine [74], triphenylphosphine [75], NaBH4 with phase transfer catalyst [76], H2S and pyridine [77], and palladium hydrox-ide/carbon with hydrazine [78], stannous chloride dihydrate [85]. 

The Stephen s method allows the reduction of nitriles by stannous chloride in acid medium. If the amine chlorhydrate initially formed is hydrolyzed, the corresponding aldehyde is obtained (37, 91). Harington and Moggridge (37) have reduced 4-methyl-5-cyanothiazole by this method (Scheme 23). However, Robba and Le Guen (91) did not obtain the expected products with 4.5-dicyanothiazole and 2-methyl-4,5-dicyanothiazole. These compounds have been reduced with diisobutyl-aluminium hydride with very low yields (3 to 6%) (Scheme 24). In other conditions the reaction gives a thiazole nitrile aldehyde with the same yield as that of the dialdehyde. 

As mentioned previously, aldehydes can be prepared by Stephen s method of reduction of nitriles by stannous chloride (37, 91). Polaro-graphic reduction of thiazolecarboxylic acids and their derivatives gives lower yields of aldehydes (58). Ozonolysis of styrylthiazoles, for example, 2-styryl-4-methylthiazole, followed by catalytic reduction gives aldehyde with 47% yield of crude product (30). 

Methylfurfural may be prepared by a modification of this method, which is more rapid but gives lower yiddsd A solution of 800 g. of sucrose in i 1. of hot water is allowed to flow slowly into a boiling solution of 500 g. of stannous chloride crystals, 2 kg. of sodium chloride, and 4 1. of 12 per cent sulfuric acid in a 12-I. flask. The aldehyde distils ofl as rapidly as it is formed and is steam-distilled from the original distillate after rendering it alkaline witlr sodium carbonate. The product is isolated by benzene extraction of the second distillate and distillation under reduced pressure. The yield is 27-35 g- (10-13 per cent of the theoretical amount). 

An alternate method of crystallization is to add all the hydrochloric acid (200 cc.) to the boiling solution and to allow this to cool slowly very large, thick needles result. In the presence of stannous chloride there is no danger of a darkening of the solution as the result of oxidation. 

The only practical method of preparing 1,4-aminonaphthol is from a-naphthol through an azo dye, the nitroso compound not being readily available. The majority of investigators have reduced technical Orange I with stannous chloride Mi.is.is.ir.is by the procedures discussed above, and benzeneazo-a-naphthol has been reduced by the same reagent. In order to make possible the use of crude, technical a-naphthol a method has been developed for the preparation of the benzeneazo compound, its separation from the isomeric dye coming from the d-naphthol present as well as from any disazo compound by extraction with alkali, and the reduction of the azo compound in alkaline solution with sodium hydrosulfite. The process, however, is tedious and yields an impure product. 

The present method is applicable with slight modifications to the preparation of both the ortho and para aminonaphthols and to many homologues, benzologues, and heterocyclic isologues of these substances. The chief feature of novelty is in the use of stannous chloride as an antioxidant in preparing and crystallizing the amine hydrochlorides. 

The latest patent for the preparation of artificial thymol is that of E. M. Cole (U.S.P. 1,378,939, 24 May, 1921). His method consists essentially in the electrolytic reduction of nitro-cymene in the presence of sulphuric acid, and the subsequent diazotisation and reduction of the para-amidocymenol produced, by e ctric action, involving the use of stannous chloride. 

Two primary types of methods have been developed to determine alkylenebis-(dithiocarbamate) residues in different crops. Both methods are based on the decomposition of the alkylenebis(dithiocarbamates) at elevated temperature in hydrochloric acid and stannous chloride to form carbon disulfide, which is analyzed by either spectrophotometry or gas chromatography (GC). 

This method was similar to that used by Hiteshue et al (3). In this method sand (50 g, mesh 0.42 - 0.15 mm) was mixed with the coal (25 g, mesh 0.5 - 0.25 mm). The addition of sand to the coal helped to prevent agglomeration (4). All the experiments used an aqueous solution of stannous chloride impregnated on the coal as a catalyst. The amount of catalyst added on a tin basis was 1% of the mass of the coal. These mixtures were placed in a hot-rod reactor and heated to 500°C at a heating rate of 200°C per minute. Residence time at temperature was 15 minutes. Hydrogen at a flow rate of 22 liters/minute and a pressure of 25 MPa was continously passed through the fixed bed of coal/sand/catalyst. The volatile products were collected in high-pressure cold traps. A schematic of the apparatus used is shown in Figure 2. 

Most of the methods for preparation of /3-naphthaldehyde have been given previously.2 A recent procedure describes the preparation of /3-naphthaldehyde from 2-bromomethylnaphthalene and hexamethylenetetramine in boiling acetic acid.3 The method of reduction of nitriles by stannous chloride was discovered by Stephen.4... 

Gill and Fitzgerald [481] determined picomolar quantities of mercury in seawater using stannous chloride reduction and two-stage amalgamation with gas-phase detection. The gas flow system used two gold-coated bead columns (the collection and the analytical columns) to transfer mercury into the gas cell of an atomic absorption spectrometer. By careful control and estimation of the blank, a detection limit of 0.21 pM was achieved using 21 of seawater. The accuracy and precision of this method were checked by comparison with aqueous laboratory and National Bureau of Standards (NBS) reference materials spiked into acidified natural water samples at picomolar levels. Further studies showed that at least 88% of mercury in open ocean and coastal seawater consisted of labile species which could be reduced by stannous chloride under acidic conditions. 

In a method described by Kiriyama and Kuroda [500], molybdenum is sorbed strongly on Amberlite CG 400 (Cl form) at pH 3 from seawater containing ascorbic acid, and is easily eluted with 6 M nitric acid. Molybdenum in the effluent can be determined spectrophotometrically with potassium thiocyanate and stannous chloride. The combined method allows selective and sensitive determination of traces of molybdenum in seawater. The precision of the method is 2% at a molybdenum level of 10 xg/l. To evaluate the feasibility of this method, Kiriyama and Kuroda [500] spiked a known amount of molybdenum and analysed it by this procedure. The recoveries for 4 to 8 xg molybdenum added to 500 or 1000 ml samples were between 90 and 100%. 

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