Weighing boat

In a thermogravimetric analysis, the sample is placed in a small weighing boat attached to one arm of a specially designed electromagnetic balance and placed inside an electric furnace. The temperature of the electric furnace is slowly increased at a fixed rate of a few degrees per minute, and the sample s weight is monitored. 

Figure 4. Plutonium oxide (2.77 micrograms) weighed on September 10, 1942. It is shown on a platinum weighing boat magnified approximately 40-fold. The Pu oxide appears as a crusty deposit (indicated by the arrow) near the end of the platinum weighing boat, which is held with forceps that grip a small handle.

To assess the reproducibility of spray volume delivery, a series of preweighed weigh boats were placed on the instrument s carousel, and the instrument was programmed to spray a single time into each. After spray delivery, the boats were reweighed, and the volume of liquid calculated. The maximum amount of fluid dispensed was 105.1 pL, and the minimum was 65.7 pL The average of 20 separate determinations was 88.8 pL, yielding an error of 11.2%. 

In general, solid solutes should be weighed on weighing paper or plastic weighing boats, using an analytical or top-loading balance. Liquids are more conveniently dispensed by volumetric techniques however, this assumes that the density is known. If a small amount of a liquid is to be weighed, it should be added to a tared flask by means of a disposable Pasteur pipet with a latex bulb. The hazardous properties of all materials should be known before use and the proper safety precautions obeyed. 

Nine spiked samples were prepared using uncontaminated wheat. Pirimiphos-methyl was applied on durum wheat grains to produce a theoretical concentration of 5 mg/kg. A layer of durum wheat grains (5 g) was deposited onto a plastic weighing boat and a solution, 250 pg/ml of pirimiphos-methyl in methanol, was added drop wise (2 pl/drop), to avoid leakage of the solution, up to 5 mg/kg concentration. After application, the plastic weighing boat was shaken to improve the mixing. The solvent was removed by evaporation at room temperature for 1 h, then 1 g of sample was randomly taken from the lot to obtain the specimen. 

To minimize contamination, the powder should be carefully placed into the weigh boat. Dropping the material from a height should be avoided. 

Unsealed containers such as weigh boats and conical beakers which contain compounds should not be removed from the powder weigh hood because the powder could become airborne during this process. 

Measure the required mass of one of the chemicals in a beaker or a weigh boat. 

Procedure Place 0.2 g of sample into a ceramic weigh boat. Mix in a small amount of comcat (100 g of tungstic anhydride and 15 g of 97% lithium metaphosphate) to facilitate combustion. Analyze the sample through the system. 

Density Measurements. The measurements were made according to the method of Archimedes. As the amount of sulfide was limited to 0.2 or 0.3 gram, the resulting loss of precision was offset by choosing a liquid whose density was as close as possible to those of the sulfides studied. The density of 1,1,2,2-tetra-bromoethane, the liquid chosen, was determined in advance as a function of temperature. The sulfides, placed in a special weighing boat, were immersed under vacuum in the apparatus shown in Figure 2. Under these conditions, the densities of the sulfides were determined with a precision of 0.2%. 

In order to make this solution, both salts should be weighed accurately using a weighing boat and transferred to a beaker. A volume less than 150 ml (let s say 100 ml) is added to the beaker and the salts allowed to fully dissolve, stirring and heating as required. This solution is then fully transferred into a volumetric flask where the volume is then accurately made up to the 150 ml mark. 

In the case of metals, the substance is contained in a weighed boat of suitable refractory material (porcelain, silica, Alundum, etc.) enclosed in a porcelain... 

Place a clean, dry weighing boat or appropriately sized sample tube onto a simple two-decimal-place balance (see p. 22) and zero (tare) the balance and weigh about 9.80 g of the chemical. 

These come in various materials, shapes and sizes from glass weighing boats to beakers and even special glazed paper. The weighing container to be used depends on several factors ... 

Fig. 4.4 Weighing containers (a) plastic weighing dishes (b) weighing bottles (c) weighing boat.

To test the precision with which 100 xL were pipeted, individually dispensed aliquots were collected into preweighed weigh boats, which... 

To assess the reproducibility of spray volume delivery, a series of preweighed weigh boats were placed on the instrument s carousel, and the instrument was programmed to spray a single time into each. After... 

The main vessels used for weighing out solids in environmental analyses are weighing bottles, plastic weighing dishes or weighing boats. These containers are used to accurately weigh the solid, using a four-decimal-place balance, and to transfer a soluble solid directly into a volumetric flask. If the solid is not totally soluble it is advisable to transfer the solid to a beaker, add a suitable solvent, e.g. deionized or distilled water, and stir with a clean glass rod until all of the solid has dissolved. It may be necessary to heat the solution to achieve complete... 

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