Potassium Dihydrogen Orthophosphate Solution

Potassium Dihydrogen Orthophosphate Solution (c). Molecular weight of KH2P04 is 136.086, atomic weight of P is 30.9738. 

The method may be standardised, if desired, with pure potassium dihydrogen-orthophosphate (see below) sufficient 1 1 hydrochloric acid must be present to prevent precipitation of quinoline molybdate the molybdophosphate complex is readily formed at a concentration of 20 mL of concentrated hydrochloric acid per 100 mL of solution especially when warm, and precipitation of the quinoline salt should take place slowly from boiling solution. A blank determination should always be made it is mostly due to silica. 

Phosphorus stock standard solution, 1000 pg P O mh (436 pg P mM) -dissolve 1.9173 g potassium dihydrogen orthophosphate, previously dried for 1 h at 105°C, in water. Transfer with beaker washings to a 1-1 volumetric flask, make up to the mark and mix. 

Potassium dihydrogen orthophosphate Sodium hydroxide solution, 1 M... 

Potassium stock standard solution, 1000 pg K mb - dry potassium dihydrogen orthophosphate (KH2PO4) for 2 h at 105°C, then allow to cool in a desiccator. Weigh 2.889 g into a 100-ml beaker, add sufficient water to dissolve, and transfer to a 1-1 volumetric flask with beaker washings make up to the mark with water and mix. 

Sodium hydride (50%, 85 mg, 1.77 mmol) was washed with dry ether (x 3) under nitrogen and suspended in dry THF (8 mL). To this suspension a solution of the hemiacetals 11 (0.52 g, 1.31 mmol) in dry THF (6 mL) was added during 5 min. The reaction was exothermic and a white gelatinous precipitate formed. After 45 min, the mixture was cooled to 0°C, quenched with cold aqueous potassium dihydrogen orthophosphate (1 M, 40 mL) and extracted with chloroform (3 x 20 mL). The combined extracts were dried (NajSO,), filtered through a pad of silica, and the filtrate was concentrated. Flash chromatography (Merck Kieselgel 60, 230-400 mesh diethyl ether-hexane, 2 1, v/v) afforded compound 12 (260 mg, 73%) as a syrup that crystallized at 5°C mp 44°-46°C, [a]D —88.3° (c 0.7, CHClj). 

Method. To 0.8 ml of the tissue extract are added 0.35 ml of water and 0.1 ml of a solution of DNS-C1 (100 mg/ml in acetone). The reaction mixture is then saturated with sodium carbonate. After reaction overnight at room temperature, 3 ml of acetone are added with shaking. The acetone phase is removed from the salts which are again washed with 3 ml of acetone. The combined extracts are neutralized with 0.15 ml of 0.066 M potassium dihydrogen orthophosphate and are then evaporated in a stream of air. The... 

The pH of the reaction medium is initially 4. In order that the pH may be maintained between 4 and 5, methyl red is added in equal concentrations to each of the three solutions any change in pH is then detected by comparison with the color of a standard solution. If necessary, the pH of the reaction medium is adjusted by adding potassium dihydrogen orthophosphate. 

KP03)3-II was first prepared by Grunze and co-workers (24). When potassium dihydrogen orthophosphate is treated with a mixed solution of acetic acid and diacetyl oxide (acetic anhydride) at 90°C. for 24 hr., almost all of it is converted into crystalline potassium trimetaphosphate (KP03)3-II. 

Heavy metal orthophosphates (M = Cr, Mn, Fe, Co, Ni, Zn, Hg, Pb, Ag) can be prepared in hydrated form by simple double decomposition involving aqueous solutions of an alkali hydrogen phosphate and the appropriate metal salt. Cobalt phosphate octahydrate, for example, is obtainable as a beautiful lavender-coloured precipitate from cobalt chloride and potassium dihydrogen phosphate. 

---