Sodium, colloidal colored

In this chapter we describe characteristic validation procedures of the Heavy Metals Limit Test in the Japanese Pharmacopoeia (JP) [1]. Although an equivalent test is commonly listed in both the United States Pharmacopoeia and the European Pharmacopoeia, there are differences in the color reagents and conditions of sample preparation of the JP procedure. Heavy metals are defined in the JP as poisonous metallic impurities such as Pb, Bi, Cu, Cd, Sn, and Hg that form colored colloidal precipitates with sodium sulfide TS in a slightly acidic solution of pH 3 to 4. The level is expressed as the equivalent quantity of lead. 

Still another method for the detection of small quantities of selenious acid consists in adding sodium hydrosulphite, NaaS jO, to the solution,2 which is then neutralised with solid sodium carbonate. The presence of the least trace of selenium causes a red coloration due to the colloidal element. 

One hundred milliliters of a 0.001% solution of tetrachloroauric (III) acid (or silver nitrate) in distilled water ia treated with several drops of 1% sodium carbonate 10-hydrate and heated to boiling in a flask. Every 30 seconds one drop of a fresh 1% tannin solution (XJ.S.P.) is added with agitation. When a deep red gold color has formed (or yellow-brown to red-brown for the silver) the colloidal solution is cooled and stabilized by the addition of a few milliliters of chloroform or toluene. 

Colloidal potassium has recently been proved as a more active reducer than the same metal that has been conventionally powdered by means of shaking it in hot octane (Luche et al. 1984 Chou You 1987 Wang et al. 1994). In order to prepare colloidal potassium, a piece of this metal in dry toluene or xylene under an argon atmosphere is submitted to ultrasonic irradiation at ca. 10°C. A silvery blue color is rapidly developed, and in a few minutes the metal disappears. A common cleaning bath (e.g., Sonoclean, 35 kHz) filled with water and crushed ice can be used. A very fine suspension of potassium is thus obtained that settles very slowly on standing. In THF, the same method did not work. Attempts to disperse lithium in THF or toluene or xylene were unsuccessful, whereas sodium was dispersed in xylene but not in THF or toluene (Luche et al. 1984). Ultrasonic waves interact with the metal via their cavitational effects (see Section 5.2.4). These effects are closely related to the physical constants of the medium, such as vapor pressure, viscosity, and sur-... 

ALCOGUM 296-W is a high viscosity aqueous solution of sodium polyacrylate. It is an anionic colloid furnished as a whitish colored homogeneous solution at 15% solids, ready for use. 

Dilute one drop of the alkaline solution with 1 mL of water and add a drop of sodium nitroprusside a purple coloration indicates the presence of sulfur. (2) Prepare a fresh solution of sodium plumbite by adding 10% sodium hydroxide solution to 0.2 mL of 0.1 M lead acetate solution until the precipitate just dissolves, and add 0.5 mL of the alkaline test solution. A black precipitate or a colloidal brown suspension indicates the presence of sulfur. 

Observation of color changes produced after addition of sodium citrate to the HAuC14 solution in the procedure used for the preparation of colloidal gold is an appropriate way to verify the adequate progress of the reaction. Initially (i.e.,... 

Gold colloids were prepared by controlled reduction of gold chloride with sodium citrate using the procedure described by Frens (15). The strength of color showing was closely related to the size and quality of the colloidal gold particles. The size of the colloidal gold particles was directly dependent on the amount of trisodium citrate used in its preparation process. The results were summarized in Table 2. 

Yellow amorphous powder, no definite mp, decomp 160 ( +216. uv max (80% methanol) 383 nm (Ej 9] 6). An amphoteric compd. Almost insol in water, benzene, chloroform, dry lower aliphatic alcohols, ether sol in basic solvents such as pyridine, collidine, and in aq lower alcohols. In coned H1S04 gives stable blue color no coloration with ferric chloride or with HO LDW i. v. in mice (using sodium carbcxymethyl cellulose as a vehicle) 6. ] 6 tng/kg, Williams et al, Antimicrob. Ag, Ckemother. 1964, 737-741. Also reported as LDjq i.v> in Swiss mice (using a colloidal suspension) 1,20 mg/kg, A. C, Parekh, C, V. Dave loc. cit. 

The sodium amide (20 mols) is prepared in 5 1. of liqmd ammonia in a 12-1. flask by the procedure described in synthesis 38, then acetylene is introduced exactly as in part B. No gas is evolved through the condenser, and the reaction mixture becomes milky with insoluble disodium acetylide, which masks the dark color imparted by colloidal iron. The milkiness persists until the theoretical amount of acetylene has been added, when the original deep-brownish or black iron color appears. Acetylene is absorbed for a few minutes longer, to saturate the ammonia solution, and is then discharged through the condenser as a final indication that the reaction is complete. 

---