Triple beam balance

A student weighs a beaker on a triple-beam balance, finding values of 50.32 g, 50.31 g, and 50.31 g in successive weighings. Express the average weight to the proper number of significant figures. 

The simplest way to determine the density of a liquid is to weigh an empty vessel of known volume and then weigh it again when it is filled with the liquid. An approximate value may be determined with a simple graduated cylinder weighed on a triple-beam balance. Only a crude value can be obtained because the balance can be read only to the nearest 0.1 g and the cylinder only to the nearest 0.1 ml. 

The next step up in a mechanical balance is the Ohaus Triple Beam Balance. The Ohaus will weigh up to 610.0 grams in 0.1 gram increments, which is more than enough for a small darkroom. 

Three types of balances are illustrated in Figs. 2.6, 2.8, and 2.10. A platform triple beam balance is shown in Fig. 2.6. This balance can weigh objects up to 610 g. Since the scale is marked in 0.1-g divisions, it is mostly used for rough weighing weights to 0.01 g can be estimated. Figure 2.7 illustrates how to take a reading on this balance. 

The single pan, triple beam balance (Centogram) (Fig. 2.8) is operated in the following way. 

Using a single pan, triple beam balance (Centogram) or a top loading balance (if available), determine the mass of the block (3). Record the mass to the nearest 0.001 g. Calculate the density of the block (4). Repeat the measurements for a second trial. 

Readability refers to the smallest measurement that a balance can indicate and that can be read by an operator when the balance is being used as intended. Generally, triple-beam balances have a readability of 0.1 g, centigram balances have a readability of 0.01 g, and analytical balances have a readability of 0.0001 g. 

The oxide characterization steps are carried out with laboratory equipment that has been adapted as necessary to facilitate handling in-cell with the manipulators. The items include a 210-yin-opening stainless steel screen assembly, a 300-g-capacity triple-beam balance, a 10-mL glass graduated cylinder and assorted weigh pans, spatulas, and oxide containers. A remotely operated calorimeter is used to assay the 244Cm content. 

If you used an electronic balance, are you certain that the digital read-out was accurate Did the last digit fluctuate at all If you used a triple-beam balance, are you certain that you read the correct value Could it have been 0.34 g or 0.32 g ... 

The powder is then placed in a protective atmosphere of dry air in a 2-1. three-necked flask fitted with a stirrer, a dropping funnel, and a safety wash bottle containing concentrated sulfuric acid. One hundred fifty milliliters of pure anhydrous dimethyl sulfoxide is added to the powdered material in the flask. Then a solution containing 200 g. (3.1 mols) of sulfur dioxide in 600 ml. of dimethyl sulfoxide is added dropwise, slowly, with stirring. Gaseous sulfur dioxide may be added to the solvent through a gas dispersion tube while weighing the container frequently on a triple-beam balance. 

Transfer the filtrate to centrifuge tubes. Be sure each pair of centrifuge tubes is carefully balanced (use a Harvard triple-beam balance) before they are placed in a centrifuge rotor. 

The single-pan electronic balance [Fig. 1 l(m)] capable of weighing to either 0.01 or 0.001 g and having a capacity of 100-250 g is very useful. Weighing is a pleasure with these balances. Although the top-loading digital balances are the easiest to use, a triple beam balance will work just as well. 

To be strictly correct we should use the word mass instead of weight because gravitational acceleration is not constant at all places on earth. But electronic balances record weights, unlike two-pan or triple-beam balances, which record masses. 

Devices used for measuring mass in a laboratory are called balances. Balances can be electronic, as shown in Figure 7, or mechanical, such as a triple-beam balance. 

Balances also differ based on the precision of the mass reading. The balance in Figure 7 reports readings to the hundredth place. The balance often found in a school chemistry laboratory is the triple-beam balance. If the smallest scale on the triple-beam balance is marked off in 0.1 g increments, you can be certain of the reading to the tenths place, and you can estimate the reading to the hundredths place. The smaller the markings on the balance, the more decimal places you can have in your measurement. 

Tools for Hand Mix-Foaming balance (electronic balance or triple-beam balance, capacity is 1 to 2 kg and sensitivity is 0.1 g) syringes for catalysts and surfactants (capacity is 5.0 ml, 1.0 ml and 0.1 ml) stirrer—spatula or glass rod high-speed electric mixer disposable wood sticks (ice-cream stick) and stop watch. 

Specific Directions. (A) Weigh out 1-0 g of benzoic acid on a triple-beam balance or on a Sanolite hand balance, and dissolve in 140... 

Ash. Shall not exceed O.Ol %. For this test, a 50g sample is weighed on a triple-beam balance into a dish, previously tated on an analytical balance, and heated over a free flame until the vapors continue oo bum after removing the frame. (During the operation the sample should be protected from drafts). When the combustion dies out, ignite the residue at low red heat (or in a muffle furnace at 800°) until the carbonaceous matter is consumed, then cool in a desiccator weigh... 

A triple-beam balance with a sensitivity less than that of a typical top-loading auxiliary balance is also useful. This is a single-pan balance with three decades of masses that slide along individual calibrated scales. The precision of a triple-beam balance may be one or two orders of magnitude less than that of a top-loading instrument but is adequate for many weighing operations. This type of balance offers the advantages of simplicity, durability, and low cost. 

Transverse wave A wave motion in which the direction of displacement is peipendicular to the direction of propagation. Triple-beam balance A rugged laboratory balance that is used to weigh approximate amounts. 

Mass The SI unit for mass is the kilogram (kg). Scientists can measure mass using units formed by adding metric prefixes to the unit gram (g), such as milligram (mg). To measure mass, you might use a triple-beam balance similar to the one shown in Figure 12. The balance has a pan on one side and a set of beams on the other side. Each beam has a rider that slides on the beam. 

When using a triple-beam balance, place an object on the pan. Slide the largest rider along its beam until the pointer drops below zero. Then move it back one notch. Repeat the process for each rider proceeding from the larger to smaller until the pointer swings an equal distance above and below the zero point. Sum the masses on each beam to find the mass of the object. Move all riders back to zero when finished. 

Figure 12 A triple-beam balance is used to determine the mass of an object.

Figure 1-11 Three types of laboratory balances, (a) A triple-beam balance used for determining mass to about 0.01 g. (b) A modern electronic top-loading balance that gives a direct readout of mass to 0.001 g. (c) A modem analytical balance that can be used to determine mass to 0.0001 g. Analytical balances are used when masses must be determined as precisely as possible.

Two instruments used to determine mass are the double-pan balance and a triple-beam balance. How each functions is illustrated in Figure 2. You can read how an electronic balance functions in How it Works in Chapter 12. 

Weigh 2 to 3 grams of sample on a triple beam balance and place it in the sample compartment of the sublimator. Save a small potion of the original material so a melting point can be obtained. 

Take a 100 mL plastic beaker, put it on a triple beam balance, and weigh into it 45 g of either your sample of ground commeal or flour or our sample. 

When the beam of the triple beam balance stops swinging, has the balance reached a dynamic or a static equilibrium Explain. 

Figure 3.1 Three examples of laboratory balances, (a) A triple-beam balance measures mass with an error of 0.01 g. It is usually used when high accuracy is not required, (b) This toploading balance measures mass with an error of 0.001 g. It has sufficient accuracy for most introductory chemistry applications, (c) An analytical balance measures mass with an error of 0.0001 g. It is usually used in more advanced courses and in scientific laboratories. 

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