Precipitation-washing method

One solution-based approach that works for gold catalysts, in that it produces highly active catalysts, is the deposition-precipitation (DP) method [8]. The DP method entails adjusting the pH, temperature, and gold concentration of an HAUCI4 solution to form a gold hydroxide species which is then deposited onto the support material [8]. This catalyst precursor is washed, dried, and annealed to form small (<5nm) catalyst particles [9]. The DP method has a number of limitations for example, DP cannot produce Au particles with diameters less than 5 nm on support materials with low-isoelectric points (lEPs) like SiOz and WO3 [5,10,11]. 

As follows from the results obtained, numerous parameters influence the quality of precipitates, vs raw materials used (such as, manganese sulphate, nitrate, chloride) pH of initial and final solutions the excess of the oxidant the type of a neutralizing agent (lithium, sodium, potassium hydroxide) the washing method, and pH of leachates. More detailed description of the synthetic routine will be published elsewhere. 

In the indirect amperometric method [560], saturated uranyl zinc acetate solution is added to the sample containing 0.1-10 mg sodium. The solution is heated for 30 minutes at 100 °C to complete precipitation. The solution is filtered and the precipitate washed several times with 2 ml of the reagent and then five times with 99% ethanol saturated with sodium uranyl zinc acetate. The precipitate is dissolved and diluted to a known volume. To an aliquot containing up to 1.7 mg zinc, 1M tartaric acid (2-3 ml) and 3 M ammonium acetate (8-10 ml) are added and the pH adjusted to 7.5-8.0 with 2 M aqueous ammonia. The solution is diluted to 25 ml and an equal volume of ethanol added. It is titrated amperometrically with 0.01 M K4Fe(CN)6 using a platinum electrode. Uranium does not interfere with the determination of sodium. 

A (Alternative) Treat 4 g (I) in pyridine with SOCl2 as described elsewhere here to get (II). Treat (II) with 2.3 g triethylamine and 2 g piperedine (or other amine) in 5 ml ether. Stir fifteen hours at room temperature extract with 200 ml water, and after precipitation, wash precipitate with 10% Na carbonate, 3N HCI and dry, evaporate in vacuum the ether solution to get (111). Reduce (111) to (IV) as above or with the NaBH4 method or possibly with hydrogenation. 

M solution. Heat the solution at 98 °C for 7 d. A compact, bright red precipitate forms. Centrifuge, wash and dry the precipitate. This method gives ca. 3 g of fairly uniform, rhombohedral crystals. 

Analysis.—Protoxide of nickel is always weighed ns such. Mix the acid solution of the oxide in a beaker glass with pure potassa, or soda in excess, heat for some time to near boiling, filter, wash the precipitate, thoroughly with hot water, diy, and ignite. The presence of ammoniacol salts, or of free ammonia, does not interfere with the precipitation This method, if carefully executed, gives exceedingly accurate results, which the Editor has often confirmed. 

The estimation of casein in milk by refractometric techniques appears to hold some promise. The casein may be precipitated, washed, and redispersed to yield a solution suitable for refractometry (Brereton and Sharp 1942 Schober etal. 1954). Another method involves computation from the difference between the refractive indices of two samples, one made alkaline to dissolve the casein and the other treated with copper sulfate to precipitate it (Hansson 1957). Heating the milk... 

The gravimetric determination of sulfate can be and is most often used to finish the Eschka and bomb washing methods. The most serious concern is that the barium sulfate precipitated may be extremely fine and difficult to filter. This can be overcome by adding the barium chloride (BaCE) rapidly to the hot solution and stirring the mixture vigorously to obtain a barium sulfate (BaS04) precipitate,... 

Removal of the precipitate from the filter If the precipitate is bulky, sufficient amounts for examination can be removed with the aid of a small nickel or stainless steel spatula. If the amount of precipitate is small, one or two methods may be employed. In the first, a small hole is pierced in the base of the filter paper with a pointed glass rod and the precipitate washed into a test-tube or a small beaker with a stream of water from the wash bottle. In the second, the filter paper is removed from the funnel, opened out on a clock glass, and scraped with a spatula. 

Vapor-phase epoxidation of propylene using H2 and O2 was carried out over gold catalysts supported on mesoporous ordered (MCM-41) and disordered titanosilicates prepared hydrothermally or by modified sol-gel method. Gold nanoparticles were homogeneously dispersed on the titanosilicate supports by deposition-precipitation (DP) method. The catalysts and support materials were characterized by XRD, UV-Vis, surface area measurements (N2 adsorption) and TEM. NaOH was found to be the best precipitant to prepare Au catalysts with optimum propylene oxide yields and H2 efficiency. The extent of catalysts washing during preparation was found to affect the activity of the catalyst. The activity and hydrogen efficiency was found to depend on the type of mesoporous support used. 

Depending upon use and stability, commercial enzymes are marketed as liquid or solid preparations. It was found that the enzyme could be recovered as a solid product by the conventional method of alcohol precipitation employed for other solid commercial enzyme products. The most efficient process was found to be evaporation of the clear filtrate to one-third original volume, adjustment of pH to 3.2 by addition of hydrochloric acid, and addition of 3.5 volumes of cold special denatured alcohol, formula 35A. The precipitate was allowed to settle, clear supernatant decanted, the precipitate washed with an equal volume of alcohol, and filtered in a filter press. The solid was washed in the press with anhydrous alcohol, blown with dry air, and finally dried in a vacuum oven at 36°C. 

Ceria was loaded on mesoporous titania by deposition precipitation (DP) method. Before deposition, the mesoporous material was suspended in water by ultrasound technique. Ceria was deposited by precipitation of Ce(N03)3 6H2O with Na2C03 at 60 °C and pH 9.0. Analytical grade chemicals were used in the support preparation. The precipitate was aged in a course of 1 h at the same temperature, filtered and washed carefully until absence of N03 ions. The sample was dried under vacuum at 80 °C and calcined in air at 400 °C for 2 h. Ceria modifying additive is 20 wt.%. The sample was labeled as CeMTi. 

Variables like the temperature of precipitation, strength of the salt solution, size of the sample, aging, rate of heating, method of washing, method of packing the sample, etc., have little effect on the thermal curves. 

In the method of Schnaase, the y-modification is obtained by introducing HgS into a cold solution of 50 g. of Mn(CH3COO)3 4HsO in 300 ml. of water. After some time, most of the sulfide settles on the bottom as a reddish-brown precipitate, while another fraction adheres to the glass wall as a beautiful, minium-red scale. The precipitate is washed with HsS-saturated water (the preferred washing method is decantation), filtered off with suction while HgS is being passed over it, washed again with alcohol and ether, and dried in an oil-pump vacuum at 80°C. 

Extract the restriction digest once each with phenol/chloroform and chloroform. After transferring the aqueous phase to an RNase-free microcentnfuge tube, ethanol precipitate, wash and dry by standard methods (16). Resuspend the pellet to between 0 25 and 1 mg/mL... 

Another method for removing interfering anions (including acetate and formate) is to precipitate the carbonate by adding calcium chloride. The precipitation, washing and isolation of the calcium carbonate can be accomplished in the bulb of the gas evolution apparatus, if the latter is placed in a centrifuge tube. 

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