Drying to constant mass

The precipitate was recovered by filtration, washed and dried to constant mass and was found to have a mass of 0-63 g. 

Example 2.3 A snspended solids analysis is run on a sample. The tared mass of the crucible and filter is 55.3520 g. A sample of 260 mL is then filtered and the residue dried to constant mass at 103°C. If the constant mass of the crucible, filter, and the residue is 55.3890 g, what is the suspended solids (SS) content of the sample ... 

We have already noted that the moisture content of some substances is substantially changed by variations in humidity and temperature. Colloidal materials containing large amounts of sorbed moisture are particularly susceptible to the effects of these variables. For example, the moisture content of a potato starch has been found to vary from 10% to 21% as a consequence of an increase in relative humidity from 20% to 70%. With substances of this sort, comparable analytical data from one laboratory to another or even within the same laboratory can be achieved only by carefully specifying a procedure for taking the moisture content into consideration. For example, samples are frequently dried to constant mass at 105°C or at some other specified temperature. Analyses are then performed and results reported on this dry basis. While such a procedure may not render the solid completely free of water, it usually lowers the moisture content to a reproducible level. 

For simple binary systems, i.e. one solute and one solvent, correction for adhering mother liquor may be made in the following manner. The damp sohd is weighed (mass mi) and then dried to constant mass, mi, at an appropriate temperature, taking care to avoid decomposition, dehydration of hydrates, etc. The amount of solvent present in the mother hquor, s (e.g. grams of solvent per gram of solution) is determined from the satimated solution analysis described above. The mass of mother hquor, m3, originaUy retained in the damp solid sample may then be calculated from... 

Water absorption. Before impregnation specimens were dried to constant mass. Tests showed that water absorption of impregnated specimens was zero, and check samples were characterized by 4.5-4.7% water absorption. 

General procedure for the desilylation of polymer supported silylated alkyues. To a suspension of polymer supported aryl trimethylsilylalkyne (1.0 eq) and THF (9 mL/g of polymer) in an Erlenmeyer flask was added a solution of TBAF (2.0 eq, 1.0 M in THF). The suspension was swirled periodically for 15 min. The polymer was then transferred to a preweighed fritted filter using THF, and washed sequentially (ca. 30 mL/g polymer) with THF followed by MeOH, and dried to constant mass in a vacuum oven at 60 °C. The efficiency of each reaction was estimated by... 

Soil samples were collected at six different locations at IPEN, using a PVC pipe with a diameter of 7.2 cm and a depth of 15 cm, after cleaning the surface manually. The quantity collected was about 500 g, and each sampling point was analyzed in triplicate. The soil samples were homogenized, dried to constant mass and passed through a sieve of 250 gm. 

To measure these properties, the test piece is dried to constant mass, weighed in air, and then transferred to an airtight dessicator, which is then evacuated until a minimum pressure is reached. After the vacuum is maintained for a set time period, the liquid is introduced until the specimens are completely covered and to ensure open pores are fiUed. In most cases distilled water is used. However, for materials that may hydrate or if assessing ex-service materials, which may contain water-soluble corrosion products, then parafiftn is preferable. 

Typically, the dispersion is dried to constant mass at a temperature of between 100 and 140 °C (see, for example, ISO 1625) and the solids content is then expressed as the percentage ratio of the dry matter to the total mass of the sample. 

A 200.0-mL sample of water was filtered through a preweighed glass fiber filter. After drying to constant weight at 105 °C, the filter was found to have increased in mass by 48.2 mg. Determine the total suspended solids for the sample in parts per million. 

In gravimetric analysis, the final product usually has to be dried completely. This is done by the process of heating to constant mass - heating the substance, allowing it to cool in a dry atmosphere inside a desiccator, then weighing it. The process is repeated until a constant mass is obtained, showing that all the water has been driven off. 

The rapid onset of polymerization is marked by a rise of the temperature to 55-60 °C and the initially clear reaction medium becomes turbid. As the reaction rate falls off, the temperature drops again to 50 °C. In the course of 45-55 min the contents of the flask change to a brown pasty mass. After 60 min the polymerization is stopped by the addition of 30 ml of butanol, thereby causing the reaction mixture suddenly to decolorize and become white. Stirring is continued fora further 10 min, and then 150 ml of meth-anolic hydrochloric acid (2 1 vol/vol) are added with stirring for another 10 min.The polymer is filtered at a Buchner funnel, thoroughly washed with methanol and acetone, and dried to constant weight in vacuum at 50 °C. 

The mass of a gravimetric precipitate is measured by weighing a dry, empty filter crucible before the procedure and reweighing the same crucible filled with dry product after the procedure. To weigh the empty crucible, first bring it to " constant mass by drying it in the... 

The normal procedure for measurement of change after exposure is to test immediately after removing the test piece from the liquid. However, ISO 1817 does allow the alternative procedure, which cannot be expected to give the same results, of drying the test pieces to constant mass at 40°C and at reduced pressure, recondition at standard laboratory temperature and then test. The question to dry or not to dry should be answered on the basis of the relevance to service and quite possibly both figures would be of interest. 

Bark samples dried at 80°C to constant mass. Bark grounded is mixed with Ca(OH), and 5% NaOH for 90 min, then extracted in Soxhlet apparatus for 7 h with toluene. Extract was evaporated to dryness under a stream of He at room temperature and diluted with mobile phase. 

SYNTHESIS A solution of 10.0 g 3-methoxy-4-ethoxybenzaldehyde in 150 mL nitromethane was treated with 1.7 g anhydrous ammonium acetate, and heated on the steam bath for 1 h. The excess nitromethane was removed under vacuum, yielding a loose, yellow crystalline mass that was filtered and modestly washed with cold MeOH. The 8.0 g of damp yellow crystals thus obtained were dissolved in 50 mL of vigorously boiling CH3CN, decanted from a small amount of insolubles (probably ammonium acetate residues) and cooled in an ice bath. The crystals so obtained were removed by filtration, washed with 2x5 mL cold CH3CN, and air dried to constant weight. The yield of 4-ethoxy-3-methoxy-B-nitrostyrene was 6.3 g of beautiful yellow crystals. 

A sample of 10.2 mg (24.4 mmol) of powdered lb was irradiated with UV light for 6 h. The resulting violet solid was then extracted with dichloromethane for 4 h to remove unreacted monomer. Drying in vacuo to constant mass gave 1.8 mg (18%) of 2b as a light-violet solid, mp >320°C. 

Find x in MgS04.xH20 or BaCl2.xH20 by thermal decomposition. Weigh a clean, dry crucible and lid. Add between 2 g and 3 g of the hydrated compound and re-weigh, then heat to constant mass. From the results calculate x. 

Determine the extractable contents of the analytes using the procedure described below. Carry out all extractions on air-dried sediment. Before subsampling, ensure the sample is suitably homogenised. Take the sample using a suitable (see Apparatus) plastic spatula. For each batch of extractions, dry a separate 1 g sample of the sediment in a layer of about 1 mm depth in an oven (105 2°C) to constant mass. From this, a correction to dry mass is obtained, which should be applied to all analytical values reported (i.e. results should be quoted as amount of metal per gram of dry sediment). Perform the extractions by shaking in a mechanical, end-over-end, shaker at a speed of 30 10 rpm and a room temperature of 22 5°C. Perform the sequential extraction according to the steps described below. 

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