Marsh test for

The hydrides of arsenic, antimony, and bismuth are unstable at elevated temperature. The Marsh test for arsenic depends on this instability when an arsenic mirror forms as arsine is passed through a heated tube ... 

Marsh test for arsenic [ARSENIC AND ARSENIC ALLOYS] (Vol 3)... 

FIG. 21-5. The Marsh test for arsenic. The sample is introduced through the thistle tube. Both arsenic and antimony produce a mirror in this test the chemical properties of the deposit permit a distinction to be made between an arsenic mirror and an antimony mirror. 

Ores of arsenic orpiment, realgar, arsenolite, arsenopyrite. Compounds of arsenic arsine, arsenic trioxide, arsenious acid, cupric hydrogen arsenite, arsenic pentoxide, arsenic acid, sodium arsenate. The Marsh test for arsenic. U.ses of arsenic and its compounds lead shot, insecticides, weed killers, chemotherapy. 

The Marsh test for arsenic involves the following steps (a) The generation of hydrogen gas when sulfuric acid is added to zinc, (b) The reaction of hydrogen with As(III) oxide to produce arsine, (c) Conversion of arsine to arsenic by heating. Write equations representing these steps and identify the type of the reaction in each step. 

By the action of nascent H upon sulfuric acid, if the mixture become heated. (See Marsh test for ai-senic.)... 

Arsine, ASH3, is much less stable than phosphine. For example, it readily decomposes upon heating to form metallic arsenic, which can be deposited as a mirror on hot surfaces. This is the basis of the once common criminological Marsh test for the presence of arsenic compounds. In practice, the contents of the victim s stomach are mixed with hydrochloric acid and zinc, producing hydrogen gas. The hydrogen in turn reacts with a variety of arsenic compounds to produce arsine that is thermally decomposed to the arsenic mirror. These processes are represented in... 

A survey of the hydrides, oxides, hydroxides, and halides highlights the network components. The hydrides of nitrogen and phosphorus emphasize the uniqueness of the lightest element. Unlike the polar ammonia, the nonpolar phosphine is a poor base and not capable of forming hydrogen bonds. Arsine is less stable than phosphine, and its decomposition is the basis of the criminological Marsh test for the presence of arsenic. 

Here then, we offer much of the descriptive aqueous chemistry in the older sources, with corrections, interpreted with the added insights and improved symbolism of recent decades, plus new information, including reactions of the recently discovered elements, but without many of the older strictly analytical techniques. Still, we mention the Marsh test for arsenic, for example, because not all laboratories around the world have the instmments that give quicker results. 

The most important interference in the Marsh Test for As is Sb, which gives stibane, SbH3, similar in many ways to ASH3. Although Ge and Se also interfere, they are so uncommon that the danger is small. Mercuiy, especially [HgCy, also fluorides and sulfites, should be absent. (The latter form H2S, which combines... 

Reduction. A sensitive test for Te involves reduction with TiCU. The released H2Te is decomposed to form a mirror as in the Marsh test for As. However, Po is precipitated fiom acids by TiCU or [SnCl3] . Both Zn and [SnCU]" in acids precipitate black Te from its compounds. 

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