Refractometric method

The refractive index of aqueous saccharose solutions varies with the concentration, and on this is based the determination of the sugar-content of a solution by means of the refractometer. 

The index of refraction of saccharine liquids may be determined by the Abbe refractometer (see Essential Oils) the reading is made if posable at 

Relation between Refractive Index and Concentration of Sugar 

1 As for as 65%, this table is taken from Schbnrock Zeitschr. des Vsr. der deut. Zucher-Ind., 1911, LXI, p. 42 the remainder is from Tolman and Smith Joum. Atner. Chem. Soc., 1906, p. 1480, and Main Intern. Sugar Joum., 1907, p. 4Sl-3 This table is calculated from the data of Schonrock (loc. cit.). 

Corrections to convert Refractive Indices at Different Temperatures 

---

Rice, F. E. and Miscall, J. 1926. Sweetened condensed milk. IV. A refractometric method for determining total solids. J. Dairy Sci. 9, 140-152. 

It must be pointed out that the hydrometric and refractometric methods are often applied to determine, in liquids containing sugars, the total solid substances (dry matter, extract), considered as if they were wholly sugar. In such cases the results have naturally a purely conventional character. 

Closer approximation is obtained by the refractometric method. For this purpose the refractive index of the juice at 200 is determined, Table X then giving the percentage of sugar, which is regarded as the dry substance the assumption here made is that the other dissolved matter influences the refractive index to the same extent as the saccharose does. 

Calculation of the Quotient of Purity.—From the results of analysis of the juice the percentage of sugar in the dry matter is calculated, this being known as the quotient or coefficient oj -purity. If the dry matter has been determined directly, this quotient is known as the real coefficient of purity, whereas, if the degrees Brix are taken as the dry matter, it is termed apparent. Further, if the dry matter is determined by the refractometric method, the optical quotient of purity is obtained, this being also an apparent coefficient, but usually nearer to the real value than the apparent coefficient calculated from the degrees Brix. 

The expression of results in analytical chemistry is mostly in SI units (all base units except the candela and many derived units). The principles to be followed to achieve the comparability and traceability of measurements to the SI have been clearly stated [1,2]. However, certain types of measurements are expressed in conventional units. Turbidity evaluation in water quality analysis, determination of soluble content of fruit and vegetable products by the refractometric method, measurement of caking power of hard coal by the Roga test, determination of the octane number of fuel and seric protein analysis are some examples. 

A chemical sensor is a device that transforms chemical information into an analytically useful signal. Chemical sensors contain two basic functional units a receptor part and a transducer part. The receptor part is usually a sensitive layer, therefore a well founded knowledge about the mechanism of interaction of the analytes of interest and the selected sensitive layer has to be achieved. Various optical methods have been exploited in chemical sensors to transform the spectral information into useful signals which can be interpreted as chemical information about the analytes [1]. These are either reflectometric or refractometric methods. Optical sensors based on reflectometry are reflectometric interference spectroscopy (RIfS) [2] and ellipsometry [3,4], Evanescent field techniques, which are sensitive to changes in the refractive index, open a wide variety of optical detection principles [5] such as surface plasmon resonance spectroscopy (SPR) [6—8], Mach-Zehnder interferometer [9], Young interferometer [10], grating coupler [11] or resonant mirror [12] devices. All these optical... 

C, equilibrium pressure cell/shake flask-refractometric method, measured range 10-110°C,... 

ASTM D542 describes two methods, viz., i) refractometric and ii) microscopic, for the measurement of refractive index of transparent organic plastics. Both the methods require optically homogeneous specimens of uniform index. The ASTM recommends that refractometric method is to be... 

For the refractometric method, the apparatus consists of an Abbe refractometer, a suitable source of white light and a small quantity of suitable contacting liquid. The test specimen for refractometer method should be 12.7x6.3 mm, with one flat face and one perpendicular surface. The two surfaces (preferably polished) shall intersect along a sharp line (without a rounded edge). The test specimen is attached to the prism of the refractometer with a drop of liquid of refractive index higher than the test specimen by at least 0.01 and it should not soften or dissolve the specimen. ASTM D542 suggests a list of liquids for a variety of plastics. Measurements are to be carried out at specified conditions, 296 2 K, and 50 5 per cent RH. Temperature is to be accurately controlled. For maximum accuracy. Sodium D lines are recommended. 

There are various methods of the glass transition temperature evaluation based on temperature dependence of polymer physical properties in the interval of glass transition 1) specific volume of polymer at slow cooling (dilatometric method) 2) heat capacity (calorimetric method),3) refraction index (refractometric method) 4) mechanical properties 5) electrical properties (temperature dependence of electric conductivity) or maximum of dielectric loss 6) NMR ° 7) electronic paramagnetic resonance, etc. 

Refractometric methods are useful for investigating vitfeous or polycrystalline silicates to determine the structural role of anions or to define Nc of cations, since the refraction of the oxide component of the silicate depends on Nc as... 

Refractometric method is especially useflil for the study of the rrans-effect in coordination compounds (see Chap. 3). In Pt(II) complexes this increases in the succession... 

Yoffe BV (1974) Refractometric methods in chemistry. Khimia, Leningrad (in Russian) Huggins ML (1941) Densities and refractive indices of liquid paraffin hydrocarbons. J Am Chem Soc 63 116-120... 

Films of 1 1 styrene-co-MA have been examined by the critical angle refractometric method.The calculated unit refractivity of 51.3 ml g agreed well with the experimental value of 50.7 ml g" The unit refractivity, which is a product of the specific refractivity and the summation of the atomic weights of the atoms in the polymer units, have been studied.The 1 1 copolymer, with a density of 1.286 (21°C), exhibited no = 1.564. ... 

Table 6-1 compares the refractive index values of different materials. Note that the refractive index of plastic materials is very close to the refractive index of glass. Two basic methods are most commonly employed to determine the index of refraction. The first method, known as the refractometric method, requires the use of a refractometer. An alternate method calls for the use of a microscope with a magnification power of at least 200 diameters. The refractometric method is generally... 

The expression (T) can be evaluated from the frequencies of the longitudinally polarized sound modes as well as from the transversely polarized ones. The accuracy of die refractive index determination by BS is comparable to that of refractometric methods. A comparison at room temperature is made in Figure 4 for optical crown glass BK-7 and for Spectrosil-A quartz. 

Kinetic curves obtained by the refractometric method (at homopolymerization of DEGBAC) are characterized by the presence of a bending in the range of the transformation degree of 10%, corresponded to the onset of the gel formation [86],... 

In this study, the effect of adhesion strength at the interface on light retraction was studied by newly developed refractometric method using the light scattering apparatus. 

---