Sodium arsenates, condensed

The working time of HT-probes decreases quickly over glass meltings with increasing temperature [55]. Vapors of the oxides, above all of sodium, potassium, silicium, lead, an-timon and arsen condense on the probe material in the temperature gradient from the inside to the outside of the tank wall. The condensed substances penetrate into the ceramic material over grain boundaries and lead to tube bursts. Thereby the stabilized zirconium dioxid is more sensitive than alumina. Componenu which contain Si02 must not be used in HT-probes [56]. 

As shown in Table 2.4, atomic absorption is extremely sensitive. It is particularly suited to the analyses of arsenic and lead in gasolines, for sodium in fuel oils (where it is the only reliable method) and for mercury in gas condensates. 

A. Triphenylarsine. In a 2-1. round-bottomed three-necked flask is placed 130 g. (5.65 gram atoms) of powdered sodium covered with 900 ml. of benzene. The flask is fitted with an Allihn condenser, a mercury-sealed mechanical Hershberg stirrer, and a 500-ml. dropping funnel in which is placed a mixture of 170 g. (0.94 mole) of arsenic trichloride and 272 g. (2.42 moles) of chlorobenzene. About 10 ml. of the arsenic trichloride-chlorobenzene mixture is dropped into the flask, and the reaction mixture is stirred and heated on a steam bath until it darkens and boils spontaneously. The steam bath is removed, and the remainder of the arsenic trichloride-chlorobenzene mixture is added drop-wise, with stirring, over a period of 1-1.5 hours at such a rate that gentle boiling is maintained (Note 1). When the addition is complete, the mixture is stirred and heated under reflux on a steam bath for 12 hours. 

The oxides and acids of antimony resemble those of arsenic, except that antimony in antimonic acid has coordination number 6, the formula of antimonic acid being HSb(OH)3. A solution of potassium antimonate, K+[Sb(OH)g], finds use as a test reagent for sodium ion sodium antimonate, NaSb(OH)3, one of the very few sodium salts with slight solubility in water (about 0.03 g per 100 g), is precipitated. The. antimonate ion condenses to larger complexes when heated this condensation may ultimately lead to macromolecular structures, such as... 

A mixture of 116 g. of arsenic acid, 220 g. of concentrated sulfuric acid, 240 g. of glycerol, and 112 g. (0.81 mole) of p-nitroaniline is heated carefully imder a reflux condenser until the onset of an exothermic reaction. When the rate of reflux has decreased considerably, heat is again applied and the reflux temperature is maintained for 2.5-3 hours. The mixture is diluted with water, allowed to stand overnight, and filtered, and the filtrate is made alkaline with sodium hydroxide. The precipitated solid is separated, dissolved in hot dilute hydrochloric acid, and treated with activated carbon. Filtration followed by saturation of the filtrate with ammonia gas precipitates crystalline 6-nitroquinoline. Recrystallization from a mixture of ethanol and water gives 98 g. (70%) of product melting at 148-149°. 

When all the dimethyl sulphate has been added, the flask is fitted with a reflux condenser and the contents boiled for 2 hours. The sodium salt of methyl arsenic acid is obtained. It is allowed to cool and a small amount of potassium iodide is added, after which a current of sulphur dioxide is passed through the liquid until it is saturated (about 6 hours). The mixture is again boiled under reflux for about an hour during this period, an oily substance consisting of methyl arsenious oxide deposits at the bottom of the flask, where it is saturated with a current of gaseous hydrochloric acid, while the flask is cooled externally. On attaining complete saturation, the flask is connected with a Liebig s condenser and the liquid distilled. Much hydrochloric acid is evolved at first later a mixture of hydrochloric acid and methyl dichloroarsine distils over. The distillation is continued until no more oily liquid condenses. The distillate is placed in a separatory funnel and the oily layer separated and distilled. 

These inconveniences may be eliminated to a great extent by using Pope and Turner s modifications. The apparatus employed by these workers consists of a vessel fitted with a reflux condenser. The sodium, freed from grease, is placed in the same vessel to which is then added the arsenic trichloride and the chlorobenzene. Benzene is employed as the solvent instead of xylene as this boils at 80° C. it maintains the temperature constant at the most favourable point for the reaction. 

Condensation of arsenic trihalides with alkyl or aryl halides in the presence of metallic sodium, analogous to a Wurtz-Fittig reaction, leads to trialkyl- and triaryl-arsines. E.g., tribenzylarsine is obtained by prolonged boiling of benzyl chloride and arsenic trichloride in ether containing sodium and a little ethyl acetate 501 tripropylarsine is obtained similarly from propyl chloride, arsenic... 

Triphenylarsine 504 Ether (600 ml anhydrous) is poured over metallic sodium (146 g fine pieces or, better, wire of diameter about 1 mm), a bulb reflux condenser is placed on the flask, and the whole transferred to a fume cupboard. A mixture of arsenic trichloride (100 g) and bromobenzene (260 g) is added fairly fast then the reaction is allowed to proceed unaided for at least 12 h, with occasional shaking, after which the solution is decanted from residual sodium and precipitated sodium halides and freed from ether. The residual oil is fractionated the arsine fraction of b.p. 220-230°/14mm is crystallized (m.p. 59°) when rubbed with ethanol. 

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