Metazin (IV) acid

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General
Surname Metazin (IV) acid
other names
  • Metatinic acid
  • Stannic acid
Molecular formula H 2 SnO 3
Brief description

white, gel-like mass

External identifiers / databases
CAS number 13472-47-4
EC number 236-745-5
ECHA InfoCard 100.033.390
Wikidata Q3604561
properties
Molar mass 168.71 g mol −1
Physical state

firmly

safety instructions
GHS labeling of hazardous substances
no GHS pictograms
H and P phrases H: no H-phrases
P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Metazin (IV) acid (tin (IV) hydroxide, tin (IV) oxide hydrate) is a chemical compound from the group of inorganic acids . Only salts are known of other tin (IV) acids, namely H 2 Sn (OH) 6 (hexahydroxotin (IV) acid) and Sn (OH) 4 ( ortho stannic acid). In addition to these salts of tin (IV) acid, there are also salts of stannic acid (II) acid, for more information see tin (II) hydroxide .

In the anions of (hexahydroxotin (IV) acid) the tin atom is octahedral surrounded by 6 hydroxyl groups.

Extraction and presentation

Tin acid is formed when a very dilute tin (IV) chloride solution is heated , when tin chloride solution is precipitated with ammonia and alkali metal stannates with an acid as a voluminous, gelatinous, translucent precipitate. After drying, it appears glassy, similar to gum arabic .

properties

Tin acid is somewhat soluble in water and is acidic. It dissolves in nitric acid and hydrochloric acid (the hydrochloric acid solution shows the properties of tin chloride), also in alkalis. With the latter, it forms soluble, readily crystallizable tin acid salts, called stannates (IV) , from which the other insoluble salts are obtained by alternating decomposition .

Under different conditions, the stannic acid changes into metazinic acid, which is also formed when tin is treated with strong nitric acid. It is colorless, has an acidic reaction and does not dissolve in nitric acid and hydrochloric acid. After treatment with hydrochloric acid, however, it dissolves in water, and from this solution it is completely precipitated by means of many salts and, after sufficient dilution with as little free acid as possible, by heating. It is more difficult to dissolve in potash and sodium hydroxide solution than Z., and when heated with a large excess of potassium hydroxide a solution is formed from which acids Z. precipitate.

Their salts crystallize with difficulty or not at all. Hydrogen sulfide, yellow tin sulfide, precipitates from the solutions of both acids. Tin acid anhydride (tin oxide) SnO 2 is found in nature as tin stone (tin ore), arises from tin chloride vapor and water vapor in red heat, forms diamond-shining, colorless crystals of the spec. Weight 6.72, which scratch glass, are insoluble in acids, but are absorbed by excess melting potassium hydrate. Amphoteric anhydride ( tin ash , Cineres Jovis) is formed when tin is continuously heated in the air, when Z is glowing, is colorless or straw yellow, tans temporarily every time it is heated, is highly fluid, non-volatile, insoluble in acids, soluble in potassium hydroxide solution . It is used as a polishing agent to represent milk glass , enamel and opaque glaze.

Of the stannic acid salts , sodium stannate ( sodium stannate , tin oxide soda, soda stannate) Na 2 SnO 3 is represented on a large scale by mixing tin with sodium nitrate and extracting the mass with water. Also by melting cassiterite (tin stone) with sodium hydroxide (caustic soda), by treating a solution of lead oxide in sodium hydroxide solution with tin, whereby lead separates out like a sponge, and by boiling lead oxide directly with tin and sodium hydroxide solution, cainic acid is obtained.

The latter method is applied to the representation of the salt from tinplate waste, which contains 3–5% tin. It forms colorless crystals with three molecules of water and is less soluble in the heat than in the cold. It is decomposed by acids, including carbonic acid in the air. It is used as a preparation salt (base salt), in dyeing and fabric printing for pickling fabrics and for anil printing , for preparing cotton mousselines de laine , for bleaching cotton yarns , and also for tinning . The metatannic acid sodium Na 2 H 8 Sn 5 O 15 , obtained by dissolving metatannic acid in sodium hydroxide solution, is white, granular, crystalline, sparingly soluble in water and, like its solution, disintegrates in metatannic acid and water when heated moderately. Tin-acid copper oxide is precipitated by tin-acid sodium bicarbonate from vitriol solution and used as a green color (gentel green).

Stannic acid salts

Stannate (IV)

Note: The name Stannate (IV) is now the common name. The salts of tin acids (II) and - (IV) used to be called stannates and stannites. The latter are now called stannates (II).

Stannate (II)

(also called stannite out of date)

Individual evidence

  1. ↑ Entry on tin acids. In: Römpp Online . Georg Thieme Verlag, accessed on April 11, 2014.
  2. ↑ Template: CL Inventory / not harmonized There is not yet a harmonized classification for this substance . A labeling of metastannic acid in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), which was accessed on May 6, 2017, is reproduced from a self-classification by the distributor .
  3. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 .

swell

from: stannic acid . In: Meyers Konversations-Lexikon . 4th edition. Volume 16, Verlag des Bibliographisches Institut, Leipzig / Vienna 1885–1892, pp. 926–927.