Direct weighing

Take approximately 0 5 g. of the finely powdered mannitol, using either a weighing bottle, or else weighing directly in the flask A as before. Heat on the water-bath for 60 minutes. During the titration with the NaOH solution, a fine precipitation of the hexacetyl-mannitol may occur, but will not affect the titration. The results are excellent. 

Standard EDTA Solutions. Disodium dihydrogen ethylenediaminetetraacetate dihydrate is available commercially of analytical reagent purity. After drying at 80°C for at least 24 hr, its composition agrees exactly with the dihydrate formula (molecular weight 372.25). It may be weighed directly. If an additional check on the concentration is required, it may be standardized by titration with nearly neutralized zinc chloride or zinc sulfate solution. 

Yeast may be suspended into a slurry and stored under refrigeration for short-time intervals to expedite its transport and metering into mixers. Water is metered into mixers rather than weighed. Minor ingredients may be weighed directly from their containers or they may be suspended in water slurries which are subsequently metered into mixers (1,3—5). 

It was found that chlorides, chlorates, and nitrates interfere by forming in sol ppts (Ref 6). Later it was found that w sol perchlorates could be analyzed gravimetrically by pptn of the perchlorate ion as tetraphenylarsonium perchlorate (Ksp at 20° = 2.60 0.14 x 10"9). The ppt can be (Tried at 105° and weighed directly (Ref 16). Still more recently a specific perchlorate ion electrode has been developed (Ref 17) which can be used for the potentiometric titration of the perchlorate ion using a soln of tetraphenylarsonium chloride as the titrant (Ref 15). Tetra-phenylphosphonium chloride has been similarly used, but the corresponding Sb compd is too insol in w for practical use (Ref 8), For routine assay of perchlorates for use by the armed forces, a Na carbonate fusion procedure is described in Mil Specs MlL-A-23946 (19 Aug 1964) MIL-A-23948 (19 Aug 1964) (see also under Ammonium Perchlorate). The tetraphenylarsonium chloride procedure has also been proposed for use in Mil Specs (Ref 11)... 

For wheat forage, hay and straw, 1.00 g of homogenized sample is weighed directly into an 11-mL extractor cell containing a paper filter disk. The sample is extracted... 

Total hydrogen also is determined by catalytic burning of a sample in oxygen It) form water. The water is absorbed in a desiccant and weighed directly. Hydrogen results as determined include the hydrogen present in both the sample moisture and water of hydration. 

In general, liquid substances of B.P. above 170° may be weighed directly into the boat. If the substance is hygroscopic the boat must be enclosed and weighed in a dry stoppered tube. Volatile... 

Because the melting point is 29.6°C, the metal may be warmed and weighed as a liquid, i Zr and Hf compounds were not investigated in the laboratory of reference 5. k Boric acid may be weighed directly from the bottle. It loses 1 H20 at 100°C, but it is difficult to dry to a constant mass. 

If it is not possible to weigh directly into a sealable vessel within the weighing hood, then the powder should be transferred into a suitable sealable container prior to removal from the weighing hood. The use of a powder funnel will ensure that the compound is appropriately transferred. A surface wipe-down of any vessel leaving the enclosure should be done. 

Weigh out between 5 and 6 g of CuCl2 record the weight to the nearest 0.001 g on your Report Sheet (1). Do not weigh directly on the balance pan, but be sure to use a container or weighing paper. 

Aluminum oxide in the sample is determined by exposing another sample of the product to a stream of dry, oxygen-free hydrogen chloride at 500°. Metallic aluminum and aluminum phosphide are volatilized under these conditions as aluminum chloride so that the residue may be weighed directly as aluminum oxide. 

Weigh directly the phenanthroline (4.95 g) in the three-necked, round-bottomed flask, add 50 mL of dry toluene and equip the flask with a thermometer, septum and water-cooled condenser. Fix the angled adaptor on top of it. 

Remove the mortar and pestle from the oven and weigh directly 1.30 g of Cs2C03 in it crush it rapidly and pour it into the round-bottomed flask. 

There is a great variety of quantitative methods available for the estimation of copper. Gravimetrically it is estimated as cupric oxide, obtained by ignition of the precipitated hydroxide by precipitation as sulphide, and ignition in an atmosphere of hydrogen to cuprous sulphide by precipitation as cuprous thiocyanate, CuCNS, this salt being either weighed directly, or converted into cuprous sulphide and by electrolytic... 

Representative for the Palladium-Catalyzed Arylation of Amines with Aryl Chlorides using (f-BuljP/Pd (Reproduced with permission from [50]. 1999 American Chemical Society) In a dry box, aryl halide, amine, Pd(dba)j, (t-BuljP, and sodium fert-butoxide were weighed directly into a screw cap vial. A stir bar was added followed by 1.0-2.0 ml of toluene to give a purple mixture. The vial was removed from the dry box, and the mixture was stirred at room temperature. After 5.5 h, the reaction mixture was adsorbed onto sihca gel and chromatographed with 50% toluene/hexanes to give 242 mg (90%) of N-(4-cyano-phenyl)diphenylamine as a white solid. 

They cannot be weighed directly without delicate apparatus and equable surroundings, hence their weight must be indirectly determined. 

Lithium ribbon (12.7 X 1.5 mm, 99.9%) obtained from Ventron Corporation (Alfa Products) was cut into thin strips after weighing directly into the tetra-hydrofuran. 

Preparing slurries for analysis. Microweighing should be done on an electronic microbalance. An amount of 1-50 mg of ground material can be weighed directly in a Teflon autosampler cup and supplied with 1.0 ml of diluent (5% sub-boiling distilled HNO, containing 0.004% Triton X-100). 

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