Chemistry in the World

1. Measurement Uncertainty Measured values vary randomly, often without apparent cause, and hence the term ‘Random errors’. The values tend to cluster around a central value, and the best estimate of this central value is the mean or average of the measured values. However, the mean may not be the 'true' value. It may be biased away from the 'true' value by a combination of errors that are essentially constant. If their values were able to be accurately determined then they could be applied as corrections to the mean, thereby bringing it into better agreement with the true value. Whilst precise determination is frequently not possible, there will usually be extreme limits that can be estimated or measured and that will encompass the possible value of such errors. These errors are called ‘Systematic errors’. Repeated measurements will not reduce the size of a systematic error or, in general, improve the knowledge of its magnitude or sign. The total error of a meas...

Indeks Refraksi berbagai Pelarut No Pelarut Indeks Reflaksi No Pelarut Indeks Reflaksi 1 Flouroalkana 1,25 26 tetrahidrofuran 1,408 2 Heksaflouro Isopropanol 1,275 27 amil alkohol 1,41 3 Metanol 1,329 28 diisobutilena 1,411 4 Air 1,33 29 n-dekana 1,412 5 Asetonitril 1,344 30 amil klorida 1,413 6 Etil eter 1,353 31 p-dioksana 1,422 7 n-pentana 1,358 32 etilbromida 1,424 8 Asetonitril 1,359 33 metilena klorida 1,424 9 Etanol 1,361 34 sikloheksana...