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for the glasses developed by Brice [15] and adopted by the U. S. Department of Agriculture for this purpose. The nearest chromaticity matches on three one-dimensional color scales (ASTM, 35Y+NR, and Gardner) are also given for each standard.

Increasing use is being made of one-dimensional photometric methods [36, 37, 162, 163] for more precise designation of sugar colors. Deitz [26] has developed a one-dimensional specification that is defined as the color difference between the solvent and the sugar solution. The color difference is evaluated in Adams chromatic-value space [2] and is expressed in terms of a so-called NBS unit of sugar color. Measurements of the attenuancy at two wavelengths (420 nm and 560 nm) are used in this evaluation to a good approximation. Brice [16] developed a similar one-dimensional specification that is based on chromaticity differences expressed in MacAdam units [19].

Table 19. U.S. Department of Agriculture chromaticity standards for sugar products. Chromaticity coordinates, x,y, for CIE source C, and nearest chromaticity matches on the ASTM, the Lovibond 35Y + NR, and the Gardner color scales

Designation and Name	Chromaticity coordinates		Nearest chromaticity match on
	x	y	ASTM color scale	Lovibond 35Y + NR scale	Gardner color scale
Liquid sugar
WW(ls), water white	0.3381	0.3529	0.35p		4.2p
W(ls), white	.3772	.3937	.75p		7.0p
EW(h), light amber	.4169	.4245	1.3 p		9.4p
Extracted honey
WW(h), water white	0.3818	0.3982	0.8 p		7.1p
EW(h), extra white	.4169	.4245	1.3 p		9.4 p
W(h), white[1]	.4786	.4531	2.1 p	4.0p	11.7 p
ELA(h), extra light amber[2]	.5317	.4450	2.9 p	7.3	13.1p
LA(h), light amber[3]	.6141	.3845	4.7	19.5g	15.85
A(h), amber	.6711	.3279	6.3	51
Maple sirup
LA(ms), light amber	0.4947	0.4509	2.35p	4.9 p	12.1p
MA(ms), medium amber	.5567	.4352	3.35	9.4g	13.7
DA(ms), dark amber	.6041	.3943	4.4	16.8g	15.5
Sugarcane molasses
No. 1	0.5183	0.4489	2.7 p	6.3	12.7p
No. 2	.6301	.3691	5.15	25 g	16.6
No. 3	.6815	.3179	6.65	64

6. Limitations of the Methods

6.1. Spectrophotometric Colorimetry

Spectrophotometric colorimetry, the most fundamental color-measurement technique, suffers from two major sources of difficulty. First, the 1931 standard observer color-matching data were obtained for only some 17 observers [61] under 2° angular subtense and quite low illumination levels. Extrapolation of the use of this system for all observers and conditions may require justification. Secondly, there is usually some lack of precision and accuracy of spectral measurement of exitance, transmittance, and reflectance. Spectrophotometrs are subject to errors of wavelength and photometric scales, stray-energy and slit-width effects, multiple reflections, and errors due to samples that are temperature dependent, wedge-shaped, and translucent. A compilation of these errors and recommendation for their accounting has been published by Gibson [35].

Although the CIE standard observer system for colorimetry has been generally satisfactory since its recommendation in 1931, there have been some difficulties with the system. Most notable is its; inability to resolve the chromaticity difference of anafase and rutile titanium dioxide [62, 71] usually viewed with angular subtense much greater than 2°. These difficulties have led the CIE to seek a new system (the 1964 CIE supplementary observer) through the Stiles and Burch [146] and Speranskaya [144] color-matching data of some 75 observers for a 10° photometric field. A complete analysis of these data permits the establishment of estimates of within and between-observer variability of the system. Estimation of the variability in the color-matching functions, r(red), g(green), and b(blue) requires information about the between-observer deviations, $\sigma _{r}$, $\sigma _{g}$, $\sigma _{b}$, the within- observer deviations, $_{w}\sigma _{r}$, $_{w}\sigma _{g}$, $_{w}\sigma _{b}$, and the covariances, $\sigma _{r}g$, $\sigma _{r}b$, $\sigma _{b}g$ The covariances, $\sigma _{i}j$, are the products of the correlation coefficients,$\sigma _{r}g$, and the deviations, $\sigma _{i}$, $\sigma _{j}$; thus $\rho _{i}j=\sigma _{i}\sigma _{j}$ where $i$ and $j$ refer to the color-matching functions. Figure 29 shows the between-observer deviations and the correlation coefficients determined by Nimeroff [123]

1. Same as Sugarcane Sirup No. 1.
2. Same as Sugarcane Sirup No. 2.
3. Same as Sugarcane Sirup No. 3.