Abstract: A method of determining or predicting a value P.sub.x of a property of a material X, which is a feed to a process or a property of a product of a process from said material or yield of said process, which method comprises measuring the absorption D.sub.i x of said material at more than one wavelength in the region 600-2600 nm, comparing the said absorptions or a derivative thereof with absorptions D.sub.i m or derivatives thereof at the same wavelength for a number of standards S in a bank for which the said property or yield P is known, and choosing from the bank at least one standard S.sub.m with property P.sub.m said standard having the smallest average value of the absolute difference at each wavelength i between the absorption D.sub.i x (or derivative thereof) for the material and the absorption D.sub.i m (or derivative thereof) for the standards S.sub.m to obtain P.sub.x, with averaging of said properties or yields P.sub.m when more than one standard S.sub.

Abstract: A method of determining or predicting a value P.sub.x of a property of a material X, which is a feed to a process or a property of a product of a process from said material or yield of said process, which method comprises measuring the absorption D.sub.i x of said material at more than one wavelength in the region 600-2600 nm, comparing the said absorptions or a derivative thereof with absorptions D.sub.i m or derivatives thereof at the same wavelength for a number of standards S in a bank for which said property or yield P is known, and choosing from the bank at least one standard S.sub.m with property P.sub.m said standard having the smallest average value of the absolute difference at each wavelength i between the absorption D.sub.i x (or derivative thereof) for the material and the absorption D.sub.i m (or derivative thereof) for the standard S.sub.m to obtain P.sub.x, with averaging of said properties or yields P.sub.m when more than one standard S.sub.

Abstract: A method of determining or predicting a value P.sub.x of a property (e.g. octane number) of a material X or a property of a product of a process from said material or yield of said process, which method comprises measuring the absorption D.sub.ix of said material at more than one wavelength in the region 600-2600 nm, comparing the said absorptions or a derivative thereof with absorptions D.sub.im or the derivatives thereof at the same wavelength for a number of standards S in a bank for which the said property or yield P is known, and choosing from the bank at least one standard S.sub.m with property P.sub.m said standard having the smallest average value of the absolute difference at each wavelength i between the absorption D.sub.i x (or derivative thereof) for the material and the absorption D.sub.i m (or derivative thereof) for the standard S.sub.m to obtain the P.sub.x, with averaging of said properties or yields P.sub.m when more than one standard S.sub.m is chosen.