Infusible white precipitate

By using a low concentration of NH3 and with no NH4+ initially present, the amide [Hg(NH2)Cl], infusible white precipitate is... 

When aqueous ammonia is added to mercury(ll) chloride, a white precipitate, the so-called infusible white precipitate of composition NH2HgCl forms ... 

Figure 20 The elementary cell of the infusible white precipitate HgNH2Br, cubic modification...

Treatment of HgCl2 with aqueous ammonia gives infusible white precipitate, HgNHgCl, containing indefinitely long chains of [—Hg—NH2—]+ with Cl ions between them in an orthorhombic structure (Fig. 282). The infusibility and low solubility is ascribed to the chain structures. 

Fig. 282. Orthorhombic cell of infusible white precipitate HgNHjCl, showing zigzag chains (—Hg—NH,—) .

A mercury(I) compound reacts with aqueous ammonia to give free mercury together with the ammine formed by the corresponding mercury (II) compound under the same conditions. Thus Hg2 l2 gives a black precipitate which is a mixture of finely divided mercury and infusible white precipitate. 

If PgCy is slowly added to a hot mixture of NH3 and the fusible white precipitate , Pg(NH3)2]Cl2, is formed, an example of (1) above. However, if NH3 is added to PgCy the infusible white precipitate , HgNH2Cl, is obtained, an example of (2) above. The addition of NH3 to Pgy or, more readily, the reaction between NH3 and Nessler s reagent , pgU] and OH, precipitates the reddish-brown iodide of Millon s base [an example of (3) above], i.e., Hg2Nl. This is a test for NH3 and is sometimes inconveniently over-sensitive. Rather similar bromides are Pg(NH3)2]Br2, HgNH2Br and Hg2NBr. 

Alkaline hydroxides yield a yellow precipitate of mercuric oxide HgO as early as pH > about 2.4. Ammonia transforms it into a yellow complex named Millon s base, with the formula [Hg2N(0H)(H20)2]. The latter, with dichloromercure(II) (wrongly called mercuric chloride ), yields white precipitate with the formula [Hg(NH2)Cl], which is called an infusible white precipitate because it volatilizes without melting. The corresponding reactions are... 

The product decomposes on sublimation forming mercury(ll) chloride, ammonia, and nitrogen. However, in the presence of ammonium chloride, the same reaction with ammonia with HgCb in aqueous solution yields fusible white precipitate, (NH3)2HgCl2. Similar product also is obtained by reaction of gaseous ammonia with solid mercury(II) chloride. However, the solid mer-cury(II) chloride is more stable than the above infusible product and can be melted without decomposition. 

Mercuric ammonium chloride 4140-42 HgNH2Cl Ammonlo-chlqrlda of mar-cury cosmetic mercury Infusible white preclpUete Lewry s white precipitate mercurammonlum chloride white precipitate. 

A tincture or infusion of galls strikes a black color and phosphate of soda throws down a white precipitate,... 

To 20 mmoles of diphenyl phosphinic acid in 300 ml of 95% ethanol is added 10 mmole zinc acetate dihydrate dissolved in 100 ml water. Then 19.7 mmole of aqueous sodium hydroxide is added and a precipitate forms. The white precipitate is filtered, washed several times with water and acetone, and dried in a vacuum oven at 110°C to give 4.2 gm (85%). The polymer is insoluble in water and common organic solvents and is infusible to above 450°C. 

Stirring is continued for one hour after all the diazo solution has been added. The mixture is now filtered and the filtrate concentrated to a volume of approximately 51. this is deep brown in color. Concentrated hydrochloric acid is added in small portions, and the tarry material which separates is filtered off. The add is added until after filtering a clear, pale yellow solution results. The phenylarsonic add is now precipitated by the addition of more hydrochloric acid. An excess must be avoided since it causes a certain amount of the phenylarsonic acid to go into solution. When this neutralized mixture has cooled, the product is filtered off and washed with a little distilled water. Small quantities of phenylarsonic acid remaining in the filtrate may be predpitated as the ferric salt by adding ferric chloride. The yield of white or cream-colored product averages more than 800 g. (50%) and in many cases runs well over 1000 g. (62%). After recrystallization from water the product is practically white and softens at 158°, passing into the infusible anhydride, C6H5ASO2. 

A tantalum compound such as the fluoride is dissolved (or suspended) in strong sulfuric acid and the mixture heated to dense white fumes on dilution Ta2Oj is precipitated. It is a white infusible powder, amorphous when first formed but becoming crystalline when heated to a high temperature. After ignition it is insoluble in all acids, but may be completely vaporized by ignition with NH[Pg.235]

Titanic acid is a snow-white infusible solid, in its relations somewhat analogous to silicic acid. When it has been fused with alkali, it becomes soluble in strong hydrochloric acid, but it is precipitated by boiling. A solution of galls causes an orange red colour in its solution, and a rod of zinc causes a purple deposit. Titanic acid is used in making the finer kinds of enamel for artificial teeth, from its whiteness and hardness. 

White mercuric precipitate (infusible) ammoniated mercuric chloride. 

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