Percentage dilutions

There are a variety of ways of preparing a set of dilutions but the two most frequently used are percentage dilutions and serial dilutions. 

In general, for the commonly used essential oils the percentage dilution is within the range 1-5%. Most aromatherapy books will describe blend compositions in terms of drops of oil, whereas a clearly defined measure such as a ml (millilitre) would be more scientific. However, this would not be very practical in practice. 

From previous experience, the BOD5 of a given type of sample is 180 mg/L. What percentage dilution should be used to analyze this sample ... 

An important additional restriction on flame structure studies of kinetics is provided by the practical problem of maintaining one dimensional flame stability over a wide range of compositions, which limits the ranges of fuel/oxidizer ratios and percentage dilution by inert additives accessible to experimental study. The advantages to the kineticist of freedom in the selection of these quantities has been stressed above. The choice of experimental conditions in flames is also limited by the direct relationship between flame temperature and initial composition. In the shock tube where heating is provided by an outside source, i.e., the shock wave, these two variables can be selected independently of one another. The instability problem with exothermic reactions in shock waves is of a different character from that in flames. 

The relative abundance of neutral SiH and H2 species have been measured as a function of power, pressure, flow rate, and dilution. For low power levels, eg, 5 W, up to 50% of the SiH gas is dissociated and the percentage increases to 80% for a power of 50 W. The decomposition of SiH gas proceeds more readily with lower flow rates. These observations, coupled with infrared (ir) measurements performed on the films, suggest that deposition under conditions in which the silane gas is not entirely decomposed leads to a majority of SiH units, whereas those deposited under conditions in which silane is strongly dissociated contain a majority of dihydride units leading to a deterioration of the semiconductor. Also, when the dwell time of SiH in the plasma region increases, the resultant film exhibits a pronounced peak at 2090 cm from the ir spectra corresponding to S1H2 inclusion. 

Generally best when crystallising component is large percentage of feed (consider preconcentration step if dilute). 

Continuous clarifiers generally are employed with dilute suspensions, principally industrial process streams and domestic municipal wastes, and their primary purpose is to produce a relatively clear overflow. They are basically identical to thickeners in design and layout except that they employ a mechanism of hghter construction and a drive head with a lower torque capability. These differences are permitted in clarification applications because the thickened pulp produced is smaller in volume and appreciably lower in suspended solids concentration, owing in part to the large percentage of relatively fine (smaller than 10 Im) solids. The installed cost of a clarifier, therefore, is approximately 5 to 10 percent less than that of a thickener of equal tank size, as given in Fig. 18-94. 

Since there is a high percentage of acetonitrile in the derivatization solution, the latter must be diluted in order to decrease the retention of the derivative in the first column and so that the derivatives can be separated from the excess reagent. The three compounds can be determined at a level of 1 p.g 1 with the sample throughput being at least 40 samples per day. 

Numbers in this column indicate oxygen percentage while the letter prefix indicates the diluent gas. For example, the entry "Cl 3" means dilution to an oxygen content of 1 3 percent with carbon dioxide as the diluent gas. The letter prefixes are C = Carbon Dioxide N = Nitrogen A = Argon and H = Helium. 

Numbers in this column indicate oxygen percentage while the letter prefix indicates the diluent gas. For example, the entry "Cl 3" means dilution... 

In one of the two cells placed back to back, the solvent, as mentioned above, was pure water in each case. When the mixed solvent in the other cell contains only a small percentage of methanol, the resultant e.m.f. will obviously be small, and it should progressively increase with increasing difference between the solvents. In Fig. 61 abscissas are values of 1/e for the mixed solvent, running from 0.0126 for pure water to 0.0301 for pure methanol. Ordinates give the unitary part of the e.m.f. extrapolated to infinite dilution. It will be seen that for KC1, NaCl, and LiCl the curves differ only slightly from straight lines, but the curve for HC1 has quite a different shape. From the experimental results on the electrical conductivity depicted in Fig. 31 we expect the curve for HC1 to take this form. In Sec. 115 we shall discuss this result for HC1, and in Sec. 116 we shall return to the interpretation of the results obtained with the alkali chlorides. 

A sample of cocaine, C17H2104N, is diluted with sugar, C H On. When a 1.00-mg sample of this mixture is burned, 1.00 mL of carbon dioxide (d = 1.80 g/L) is formed. What is the percentage of cocaine in this mixture ... 

The available chlorine refers to the chlorine liberated by the action of dilute acids on the hypochlorite, and is expressed as the percentage by weight in the case of bleaching powder. Commercial bleaching powder contains 36-38 per cent of available chlorine. 

Take some crude cresol mixture (1 g) and dissolve it in cyclohexane (20 mL). Obtain the infrared spectrum for the mixture if necessary, dilute the solution further with cyclohexane to obtain absorbances which will lie on the calibration graphs. From the selected absorption peaks calculate the absorbances for the three individual isomers and use the calibration graphs to calculate the percentage composition of the cresol mixture. 

Take 10 mL of commercial propan-2-ol and dilute to 100 mL with carbon tetrachloride in a graduated flask. Record the infrared spectrum and calculate the absorbance for the peak at 1718 cm-1. Obtain a value for the acetone concentration from the calibration graph. The true value for the acetone in the propan-2-ol will be 10 times the figure obtained from the graph (this allows for the dilution) and the percentage v/v value can be converted to a molar concentration (mol L-1) by dividing the percentage v/v by 7.326 e.g. 1.25 per cent v/v = 1.25/7.326 = 0.171 molL-1. 

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