Heating the Sample

The appropriately clamped thermometer is set up in the Thiele tube as in (Fig. 39). Look at this figure now and remember to heat the tube carefully— always carefully—at the elbow. Then  

If you don t know the melting point of the sample, heat the oil fairly quickly, but no more than 10° Cper minute to get a rough melting point. 

And it will be rough indeed, since the temperature of the thermometer usually lags that of the sample. 

After this sample has melted, lift the thermometer and attached sample tube carefully (it may be HOT) by the thermometer up at the clamp, until they are just out of the oil. This way the thermometer and sample can cool, and the hot oil can drain off. Wait for the thermometer to cool to about room temperature before you remove it entirely from the tube. Wipe off some of the oil, reload a melting point tube (never remelt melted samples), and try again. And heat at 2°C per minute this time. 

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Before withdrawing a sample it is necessary to agitate it, even if it is a gas, and eventually heat the sample being careful to stay below temperatures which could cause evaporation of the lighter components. 

As a final example, the determination of carbon in steels and other metal alloys can be determined by heating the sample. The carbon is converted to CO2, which is collected in an appropriate absorbent trap, providing a direct measure of the amount of C in the original sample. 

Dielectric Strength. Dielectric failure may be thermal or dismptive. In thermal breakdown, appHed voltage heats the sample and thus lowers its electrical resistance. The lower resistance causes still greater heating and a vicious circle, leading to dielectric failure, occurs. However, if appHed voltage is below a critical value, a stabilized condition may exist where heat iaput rate equals heat loss rate. In dismptive dielectric failure, the sample temperature does not iacrease. This type of failure is usually associated with voids and defects ia the materials. 

It has been reported that exchange of protons activated by enolization can be performed directly in a glass inlet system of the mass spectrometer prior to analysis by heating the sample at about 200° with deuterium oxide vapor for a few minutes. " Exchange has been observed with 2-, 3-, 6-, 11- and 17-keto steroids, but the resulting isotopic purity is usually poor,... 

It is obviously desirable that the time required to heat the sample solution be... 

Dinitro-6,6 -diphenic acid can actually be resolved into two enantiomeric forms, but heating the samples causes them to racemize. Explain. 

N 22.08%, OB to C02 -52.96%, cryst, mp 96-97° (Ref 3). Prepd from 2,3,4,6-tetra-nitrophenylmethylnitramine and m-nitrotetryl upon heating with methyl alcohol (Refs 1 2). The expln temp (187°) was obtd on heating the sample at the rate of 5°/min, while a temp of 198° was detn by heating at the rate of 20°/ min (Refs 2 3). Impact sensitivity with the Kast app, max fall for no detonation using a 10kg wt (6 shots) was 15-16cm vs 14cm for... 

From the results of the urease activity test summarized in Figure 15, it is clear that the deposition procedure preserved to a certain extent the enzyme catalytic activity. Heating the sample before testing decreased the enzyme in the film by about 30% but did not eliminate it completely. The results of the activity test of two samples are summarized in Table 1 together with reference values for a spontaneous reaction without enzyme. It is necessary to underline that enzymatic activity on spherical supports was higher than the respective value in flat films, which could indicate that apparent catalytic efficiency was improved due to an increased area-to-volume ratio. 

Physical properties of the prepared catalysts were measured by an adsorption analyzer [Quantachrome Co., Autosorb-lC]. The structure of prepared catalysts were investigated by XRD [Simmazdu Co., XRD-6000] with a Cu-Ka radiation source (X = 1.54056 A), voltage of 40.0 kV, ciurent of 30.0 mA and scan speed of 5.0 deg/min. Also, temperature-programmed reduction (TPR) profiles of the samples were investigated by a sorption analyzer [Micromeritics Co., Autochem II] and obtained by heating the samples from room temperature to 1100°C at a rate of lOTl/min in a 5 % H2/Ar gas flow (50 ml/min). 

Dynamic headspace GC-MS involves heating a small amount of the solid polymer sample contained in a fused silica tube in a stream of inert gas. The volatile components evolved on heating the sample are swept away from the sample bulk and condensed, or focused on a cryogenic trap before being introduced onto the chromatographic column via rapid heating of the trap. The technique can be used qualitatively or quantitatively DHS-GC-MS is considered to be well suited towards routine quantitative analysis. 

After the catalyst was saturated with carbon dioxide, a temperature programmed desorption (TPD) was carried out by heating the sample in helium (40 cm3min 1) from room temperature to 873 K (10 Kmin 1). The mass spectrometer was used to follow water (mass 18), carbon monoxide (mass 28), carbon dioxide (mass 44) and oxygen (mass 32). 

Heating the sample with a conventional heat source or a laser and measuring the intensity of the luminescence emitted by the sample. 

Dissolution procedures are described for gram samples of graphite or pyrolytic carbon, milligram samples of irradiated fuel particles, and for more readily oxidised forms of carbon, such as charcoal. The first two methods involve heating the samples with mixtures of 70% perchloric and 90% nitric acids (10 1), and must only be used for graphite or pyrolytic carbon. Other forms of carbon must not be oxidised in this way (to avoid explosions), but by a preliminary treatment with nitric acid alone and in portions. 

Thermal decomposition of palladium acetate, either by laser irradiation or conventional means, leads to complete volatilization of the organic components. The purity of the ion beam-irradiated samples is significantly improved by heating the samples in hydrogen at 300 °C after removal of unirradiated palladium acetate. 

Fig. 7.8 SEM (A-C) and TEM (D-F) images of (PAA/PAH)2/PAA NPS at different magnification. PAA (2000 g mol-1) and PAH (15 000 g mol-1) were deposited from 5mgmL-1 solutions containing 0.7 M NaCI at pH 2.9 and 4.3, respectively. Cross-linking was applied after the deposition of each layer by heating the samples...

The optimal concentration of NaOH or KOH is 0.1 M. Lower concentrations, such as 0.01 M NaOH or KOH, gave obviously poorer results. Rudbeck and Dissing30 extracted DNA from whole blood by heating the sample in NaOH solution in order to dissolve the blood pellets and found that >0.1 M NaOH at >70°C completely dissolved the pellet in 5 min, whereas 0.02 M NaOH had no effect even after incubation for 24 h. Our results indicated satisfactory dissolution of archival tissue sections when using 0.1 M NaOH as retrieval solution. 

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