Licence: Public Domain Mark
Credit: Qualitative chemical analysis / by C. Remigius Fresenius. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
124/526 page 100
![fore promotes the separation and increases the quantity of the pre- cipitate. Chloride of ammonium and similar salts of ammonia, when present in sufficient quantity, prevent this precipitation, and also readily redissolve the precipitates after they have been washed. 7. If solutions of magnesia are mixed with carbonate of ammonia, the liquid always remains clear at first; but after some time, it deposits a crystalline precipitate, more or less quickly according to the concen- tration of the solution. When a small quantity only of carbonate ot ammonia is added, the precipitate consists of carbonate of magnesia, MgO,C02 + 3aq [MgCOa.SH.O], but when the carbonate of ammonia is in large excess, it consists of carbonate of magnesia and am- monia, MgO,CO, + NHp,CO, + 4aq [Mg(HN,),(0O3)„4H,O]. This pre- cipitate is not formed in very dilute solutions. The addition of ammonia and of excess of carbonate of ammonia promotes its separation, whilst cliloride of ammonium hinders it; it does not, however, prevent the for- mation of the precipitate in very concentrated solutions. 8. PhosptLate of soda added to solutions of magnesia, if they are not too dilute, precipitates phosphate of magnesia, 2MgO,HO,P05 + Uaq [MgHP0„7H,0], as a white powder. On boiling, basic phosphate of magnesia, 3MgO,P05 + 7aq [Mg3(P04)„7H,0], separates, even from rather dilute solutions. If the addition of the precipitant is, however, preceded by that of chloride of ammonium and ammonia a white crystalline precipitate of basic phosphate ot magnesia and ammonia, ,k,u ^D^^ ru m 2MgO,NHp,PO,+ 12aq [Mg(NH,)P0„6H,0], ^ will be thrown down even from very dilute solutions of magnesia; its separation may be greatly promoted and accelerated by stirring with a glass rod: even should the solution be so extremely dilute that no precipitate is formed, yet the lines of direction m which the glass rod has moved along the side of the vessel will after the lapse of appear distinctly as white streaks (soluble in hydrochloric acid) Watei and solutions of salts of ammonia dissolve the precipitate but very sliehtlv • it is, however, readily soluble in acids, even m acetic acid, it mav be considered as insoluble in water containing ammonia. 9 Oxalate of ammonia produces no precipitate in very dilute solutions of magnesia; in less dUute solutions no precipitate is formed at first but after some time, crystalline crusts of various ammonia magnes a oxalates make their appearance. In highly concentrated Sons oxalate of ammonia very speedily produces a precipitate _ of soiuuons, uAciicxt _ QMrrO r O 4-4ari rMgC.,04,2H„0], which contams oxalate of magnesia, 2MgO,^U6-i-4aq L 6 ^ 4. 2 J' , small quantities of the above-named double salts, /^f ^^^^l^^f ^ monium especially in presence of free ammoma, interferes with the f~on ofTheVpreci'pitates, but does not usually entirely p-^^^^^^ it^ ^0 Sulphuric acid, hydrofluosilicic acid, and chromate of potassa do not precipitate salts of magnesia. 11. Salts of magnesia do not colour flame.](https://iiif.wellcomecollection.org/image/b21966953_0124.jp2/full/800%2C/0/default.jpg)
