Standard weighing

Assay Preparation For Pancreatin having about the same amylase activity as the USP Pancreatin Reference Standard, weigh accurately about 40 mg of Pancreatin into a suitable mortar. 

To prepare. Vitamin C standard. Weigh 50 mg of /-ascorbic acid to the nearest 0.1 mg, dissolve in a 50-mL volumetric flask, and dilute to yolume with distilled deionized water. Prepare the day of use. This is a 0.1% solution. Prepare serial dilution of this to obtain also 0.05% and 0.02% standards. 

From 1838 to 1843 he was constructor and cmator of the standard weighing apparatus of the US Mint,... 

Besides the standard weighing methods, it has also been proposed to use the piezoelectric properties of quartz for mass determination. Change in the weight of a sample that has been deposited direcdy on the quartz surface, causes a change in the oscillation frequency of the quartz crystal. Mass changes as small as 10" g can be determined by this method. The changes in frequency with temperature must be established by calibration, or the experimentation must be done isothermally. 

W2 = mass of compound Z (pure calibration standard or internal standard) weighed out to prepare a solution for ealibration and/or spiking ... 

Here Xj-x represent measured quantities including physical ones (e.g., mass of analytical standard weighed out, volumes of standard flasks etc.) and chemical properties (e.g., chemical purity of analytical standard, isotopic purity of an internal standard, ratios of analytical signals for analyte and internal standard etc.). Specific examples of such functions are those discussed in Section 8.4. The experimental variables (x(m+])-x ) that do not appear directly in the functional relationship could include temperature of various components of all forms of apparatus used, mobile phase composition and flow rate, operating parameters of the mass spectrometer, etc. 

A stock solution was prepared by dissolving the enriched isotope. Diluted solutions were prepared from this stock solution on a weight basis. The isotopic composition of this solution was determined experimentally by GC-MS analysis of the chelate. The internal standard solution was calibrated by reverse isotope dilution GC-MS using the atomic absorption primary standard. Weighed amounts of the primary standard solution were mixed with weighed amounts of the enriched isotope solution. Chelates were prepared from the spiked samples (as described below) and were used for mass spectrometric determination of isotope ratios. Concentration of the trace metal in the spike solution was calculated using the experimentally determined isotope ratios, the weights of the standard and... 

Prepare individual standards of alanine, arginine, leucine, and valine (Sigma) as 1 pg/pl solutions in deionized water. Prepare each standard by dissolving 10 mg of an amino acid in 10 ml of water. Prepare a mixed standard of the four amino acids at 1 pg/ J.l for each. To obtain the mixed standard, weigh 10 mg of each amino acid and dissolve in 10 ml of water. 

Full characterization of hydrogen absorbing materials requires the determination of the hydrogen concentration. For bulk materials this is not a particular problem since even standard weighing techniques will often suffice. Thin films present more difficulty simply because of the small amount of material available. The purpose of this paper is to describe two techniques which are useful for measuring hydrogen concentration in thin films. We will describe their application to the palladium-hydrogen system. 

XI. 1.2.3 Similarly, add isopentane, n-butane, isobutane, propane, ethane, and carbon dioxide, in that order, as desired, in the reference standard. Weigh Cylinder A after each addition to obtain the weight of the component added. Connect Cylinder A to the evacuated 20-L cylinder with as... 

The prime global authority is the International Maritime Organisation. The IMO sets the standards and guidelines for the removal of offshore installations. The guidelines specify that installations in less than 75 meters of water with substructures weighing less than 4,000 tons be completely removed from the site. Those in deeper water must be removed to a depth of 55 meters below the surface so that there is no hazard to navigation. In some countries the depth to which structures have to be removed has already been extended to 100m. 

A rugged, powerful instrument in a cast aluminium case Weighs 6 kg including standard D cell batteries... 

Addition of silver nitrate to a solution of a chloride in dilute nitric acid gives a white precipitate of silver chloride, AgCl, soluble in ammonia solution. This test may be used for gravimetric or volumetric estimation of chloride the silver chloride can be filtered off, dried and weighed, or the chloride titrated with standard silver nitrate using potassium chromate(VI) or fluorescein as indicator. 

The difficulties of working with small quantities of liquids are much greater than with small quantities of solids. For example a competent worker can, and does in fact, often work with 100 mg, of solid without any special apparatus. With liquids this is often not practicable because of the much greater losses entailed, particularly when it is realised that one ordinary-sized drop weighs about 50-100 mg. The account which follows gives details of modifications of standard apparatus suitable for the semi-micro scale defined above. 

Weigh out accurately about 1 25 g. of the sample, dissolve it in water and make the solution up to 250 ml. Titrate this solution against 25 ml. of the standard Fehling s solution, precisely as before. 

Provided that the balance is functioning correctly, the main source of error is in the weights themselves these should be calibrated by one of the standard methods so that their relative values are known, and they should be carefully cleaned with tissue paper and checked from time to time. To make the best use of the balance, weighing should be carried out by the method of swings, but for this purpose it is necessary first to determine the sensitivity of the balance. 

Hydrazine hydrate may be titrated with standard acid using methyl orange as indicator or, alternatively, against standard iodine solution with starch as indicator. In the latter case about 0-1 g., accurately weighed, of the hydrazine hydrate solution is diluted with about 100 ml. of water, 2-3 drops of starch indicator added, and immediately before titration 6 g. of sodium bicarbonate are introduced. Rapid titration with iodine gives a satisfactory end point. 

The m.p. is not always a safe criterion of purity. Benzoyl peroxide may be analysed as follows -. Dissolve about 0-6 g., accurately weighed, of benzoyl peroxide in Is ml. of chloroform in a 350 ml. conical flask. Cool to — 5°, and add 25 ml. of 0- IN sodium methoxide solution at once with cooling and shaking. After 5 minutes at — 5°, add 100 ml. of iced water, 5 ml. of 10 per cent, sulphuric acid, and 2 g. of potassium iodide in 20 ml. of 10 per cent, sulphuric acid in the order mentioned with vigorous stirring. Titrate the liberated iodine with standard 0-lN sodium thiosulphate solution. 

To determine the exact diazomethane content, allow an aliquot portion of the ethereal diazomethane solution to react with an accurately weighed amount (say, about 1 g.) of A. R. benzoic acid in 60 ml. of anhydrous ether. The solution should be completely decolourised, thus showing that the benzoic acid is present in excess. Dilute the solution with water and titrate the excess of benzoic acid with standard 0 IN alkali using phenolphthalein as indicator. 

Some scientific studies indicate that the gam in performance obtained through the use of anabolic steroids is small This may be a case though in which the anecdotal evidence of the athletes may be closer to the mark than the scientific studies The scientific studies are done under ethical conditions in which patients are treated with prescription level doses of steroids A 240 pound offensive tackle ( too small by todays standards) may take several ana bolic steroids at a time at 10-20 times their pre scribed doses in order to weigh the 280 pounds he (or his coach) feels is necessary The price athletes pay for gams in size and strength can be enormous This price includes emotional costs (friendships lost because of heightened aggressiveness) sterility testicular atro phy (the testes cease to function once the body starts to obtain a sufficient supply of testosterone like steroids from outside) and increased risk of prema ture death from liver cancer or heart disease... 

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. 

Th(N03)4 4H3O 552.12 Weigh the appropriate amount of crystals and dissolve in water. Standardize against NaF. 

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