Average content sample size

TABLE 13—Average uranium ( /) and radium (Jia) contents of sized samples of phosphogypsum, pCi/g. 

The hydrogen content varies widely fi om almost zero to values more nearly typical of organic compoimds, but in general, relatively large sample sizes are needed, usually in the 10—20 g range. This has the advantage that it ensures that a macroscopic average is measiued so the spectrum is representative of the bulk of the sample. 

Platinum and chlorine (samples made with chloride precursors) contents of the catalyst samples were determined with X-ray fluorescence spectroscopy (XRF) (Phillips PW 1480 spectrometer). BET surface areas of catalysts were within 5% that of the silica support material. Platinum dispersion was measured with hydrogen chemisorption in a volumetric set-up, using a procedure described elsewhere [3]. Stoichiometry of H/Pt = 1 was assumed for calculating the platinum dispersion [4]. Transmission electron microscopy (TEM) (Phillips CM 30, 300kV) was used to check the platinum particle size in some of the catalysts. Average platinum particle size was determined based on analysis of about 100 platinum crystallites. 

In the hydrogenation of cinnamaldehyde over the same Ru/C catalysts, selectivity to cinnamyl alcohol changed with Ru content. The influence of Ru loading on the selectivity to cinnamyl alcohol is reported in Fig. 1. The highest selectivity to cinnamyl alcohol was observed on the 10 wt.% Ru sample. On the Ru/C samples an increase of the Ru loading results in the formation of larger Ru metal particles. This is supported by the chemisorption data, which show a decrease of the CO/Ru ratio (table 1), and by a TEM analysis [2] which has shown that the average Ru particle size increases from 3 nm on the 0.5 wt.%... 

Early thermal-conductivity measurements on CVD diamond were performed on relatively thin films (less than 30 pm) with average lateral grain sizes of only a few micrometers, grown by MWP-CVD [71] or HF-CVD [72]. For both growth methods the in-plane thermal conductivity [ decreased from about 10 to less than 2Wcm K , if the methane concentration in the source gas was increased to several percent, accompanied by a deterioration of the film quality as to be judged from Raman spectra and (in the case of the HF-CVD samples) an increase of the H-content from 0.1 to 1.0%. 

For determination of the average content of pharmacy preparations the sample size has to be sufficiently large for a statistically significant conclusion. With preparations in which the active substance is dissolved, then problems with uiuformity of content (see also Sect. 32.7) should be rare and therefore smaller samples will give a suitable level of... 

Consider the two density functions in Fig.21.8 from a different point of view. The first is the density function of the sample average when the sample size is 1. The second when the sample size is 2. As the sample size increases, the graph becomes more like the bell-shaped curve for the normal distribution. This is the content of the Central Limit Theorem in the next section. As the sample size increases, the... 

Figure 4.40. Content uniformity samples (10 each) taken from the beginning, middle, and end of a production run and each assayed for the compounds A and B. The results were sorted according to size both the slopes and the averages are very similar and well within the allowed range.

Sample Average size [pm] Speiafic gravity [gem j DVB Content [wt%] Remarks... 

---