Perceptible Color Change Research Articles

The suitability of SunCheckR patches and TanscanR cards for monitoring the sunburning effectiveness of sunlight

UV-sensitive products which undergo a colour change on exposure to UV radiation are available for use by the general public. We have evaluated SunCheck patches of various sensitivities, and Tanscan UV sensor cards, in terms of their temperature stability, wavelength response and response to sunlight. The products exhibited no perceptible colour change when the temperature was maintained at 45 degrees C for 4 hours; on exposure to monochromatic radiation, the sensitivity peaked at a wavelength of 335 and 355 nm for SunCheck and Tanscan, respectively; the response to sunlight under clear conditions was reasonably consistent, with the coefficient of variation for each type of material ranging between 12.5 and 27%. These products are based on the incorrect concept that there is a 'safe' dose of UV radiation. Thus, they cannot be recommended to the public as a reliable way of reducing the risk of skin cancer.

Synthesis and characteristic properties of poly(naphtho)[2,3- c] thiophene) as a series of fused-ring conducting polymers analogous to poly(isothianaphthene)

Naphtho[2,3- c]thiophene was easily obtained as a yellow solid containing 1,3-dihydronaphtho[2,3- c]thiophene as a by-product through dehydration of 1,3-dihydronaphtho[2,3- c]thiophene 2-oxide by refluxing with neutral alumina in deoxygenated methylene chloride solution. Naphtho[2,3- c]thiophene was electrochemically polymerized by a well-known technique to form a thin film of poly(naphtho[2,3- c]thiophene) (PNT) which showed barely perceptible color changes associated with the electrochemical doping at a redox potential of ≈0.69 V versus Ag/AgCl. An opto-electrochemical study revealed that the band gap ( E g) of PNT was 1.5 eV, whereas it had been previously expected from theoretical calculations to be nearly zero eV.

Storage of milk powders under adverse conditions. 2. Influence on the content of water-soluble vitamins.

Storage of milk powder under unfavourable conditions accelerates the normally slow deterioration in nutritional quality. The effects of such storage on the water-soluble vitamin composition were examined. (a) Spray-dried whole milk containing 25 g water/kg was stored at 60 degrees and 70 degrees and sampled weekly to 9 weeks. (b) Spray-dried whole milk and skimmed milk were adjusted to contain 40 and 100 g water/kg and stored at 37 degrees in nitrogen and in oxygen. Samples were taken for analysis at intervals during storage. The samples were analysed for eight B-complex vitamins and ascorbic acid, and also for total lysine, 'reactive lysine' and 'lysine as lactulosyl-lysine'. Storage at 60 degrees caused rapid destruction of folic acid (53% loss at 4 weeks) and slower loss of thiamin, vitamin B6 and pantothenic acid (18% at 8 weeks). There was no change in the content of riboflavin, biotin, nicotinic acid and vitamin B12. At 70 degrees the rate of destruction of the four labile vitamins was much increased; 18% or less survived at 4 weeks. At 37 degrees and 40 g water/kg there was little change in total and 'reactive' lysine during storage for 57 d. Lactulosyl-lysine was demonstrably present but at low concentration. There was considerable loss of folate (72%) and ascorbate (91%) during storage for 30 d in O2, but no significant loss in N2. Thiamin fell by approximately 12% in 57 d, equally in O2 and N2. The content of the remaining vitamins was unchanged. At 100 g water/kg there were progressive Maillard changes. During 27 d in N2 the colour changed from cream to pale brown, but in O2 there was no perceptible colour change. Total lysine fell by 20% in 27 d, and 'reactive lysine' by 30%. Folate was stable during 16 d in N2, but largely (94%) destroyed in O2. Ascorbic acid was also destroyed in N2 as in O2. Thiamin fell by 41% in 27 d, equally in O2 and N2. Vitamin B6 was more labile, especially in N2, falling by 71% in 16 d. With skimmed-milk powder containing 100 g water/kg, storage at 37 degrees in O2 and N2 gave much the same results as for the corresponding whole-milk powder. The presence of milk fat had no marked effect on the stability of the water-soluble vitamins. Destruction of vitamins was clearly linked to the progress of Maillard-type reactions and was strongly influenced by time and temperature of storage, moisture content and, in some instances, by the presence of O2.

ツユクサの青色メタロアントシアニンの結晶化と その性質とについて

(1) A blue anthocyanin was isolated in crystalline state from the petals of “Awobana”.plant (Commelina communis L, var. hortensis Makino) (cf. Fig. 1), and was shown to be identical in all respects with the blue crystals previously obtained from the petals of wild commelina (Commelina communis L. var. communis). We propose the name “commelinin” for this blue anthocyanin.(2) Commelinin seems to be a high molecular compound, which is non-dialysable through semi-permeable membranes. The estimation of the individual components gave the following results: p-coumaric acid 11.83%, delphinidin (as chloride) 27.33% and glucose 30.78%, Mg 0.42%, K 1.47% and Na 0.29%, respectively. Probably, Na is not inherent to the pigment molecule.(3) On treatment with 1% hydrochloric acid, commelinin loses its alkali metals altogether. The resultant product, which is still bound with Mg as before, is also convertible into brilliant blue crystals (cf. Fig. 4). Therefore, it is concluded that the blue color of commelinin is not due to an alkali phenolate of anthocyanin.(4) Mg remains fixed to the pigment molecule even after treatment either with EDTA or cation exchangers. Of course, no perceptible color change occurs in these cases.(5) Besides, commelinin seems to contain an appreciable amount (25-30%) of an unknown substance, which is pale yellowish in color and is presumed to be a flavonoid.(6) To sum up the analytical results obtained, commelinin is a co-ordination compound, in which one atom of Mg combines four molecules of awobanin (delphinidin-3: 5-dimonoglucoside+p-coumaric acid) around it, and an unknown flavonoid-like substance is further brought into association with it (cf. Table 3 and 4).

Two New Total Alkalinity Indicators

ries have been suggested for the total alkalinity titration of water (1). One of these undergoes an orange-red to bluish-purple transition, while the second changes from a deep yellow to a muddy hue. . Among the advantages claimed for these dyes is that their greatest color responses occur in a pH range where methyl orange fails to function. Moreover, the color responses are of an order which can readily be reproduced by most analysts. As Cooper (2) and other investigators have shown, methyl orange is sometimes unsuitable for the determination of low alkalinities. Schroeder (3) states that the phenolphthalein-methyl orange titration is not accurate in boiler-water solutions whose concentrations of carbonates are below 60 ppm. At 30 ppm. of carbonate the maximum possible error which may be expected is 26 per cent. This error arises largely from the fact that the first perceptible color change with methyl orange occurs at a pH of 4.6. According to Cooper (2), the pH prevailing at the end-point of an acid-carbonate titration of 30 and 50 ppm. should be 4.85; for 70 and 100 ppm. the pH should be 4.75; for 150 ppm., a pH of 4.6; and for 250 ppm., a pH of 4.5. Thus, methyl orange under the most favorable circumstances is only justified for alkalinities in excess of 150 ppm. Many individuals possess imperfect color sensibility, however, rendering impossible the proper identification of he faint orange characteristic of methyl orange at a pH of 4.6. Often the sample is overtitrated to a deeper orange representing a pH of 4.5 or 4.4, with a consequent sacrifice in accuracy. Other considerations also contribute

A sensitive method for measuring carbon dioxide.

The most sensitive method hitherto used for measuring the carbon dioxide output of tissues in vitro is the method of Tashiro,1 depending upon the detection of a crystal of barium carbonate in a solution of barium hydroxide under the microscope. It was found that 1 × 10-7 of a gram of carbon dioxide gave a visible precipitate in 10 minutes. An unknown amount of carbon dioxide was measured by rinding such a dilution that a visible precipitate was just formed in 10 minutes. This method has not been found useful in practice in the hands of others.The next most sensitive method is the indicator method of Osterhout,2 which in the hands of Parker3 has been found adequate for the detection of 1 × 10-6 grams. It takes, however, 20 × 10-6 grams to produce the standard color change in the indicator. If this change takes place in 20 minutes, Parker finds himself able to detect a perceptible color change after 1 minute, i. e., from the effect of 1 × 10-6 grams.At the Cleveland meeting of the Federation, December, 1925...