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262 History of Three-Color Photography
one at C^D to D, and a broad minimum in the green. It will not stand the addition of ammonia, and presents no particular advantage.
Pinachrom Violet90 which is a true isocyanin, was discovered by E. Staehlin of Meister, Lucius & Briining, and can be combined with pinaverdol and pinachrom much better than pinacyanol, and then gives greater sensitiveness in the red. It is very sensitive to acids, and when diluted with water is bleached by carbonic acid. It can be used in exactly the same way as pinacyanol in a bath of :
Pinachrom violet, 1 : 1000 ale 10 ccs.
Orthochrom T, 1 : 1000 ale 10 ccs.
Or pinaverdol, 1 : 1000 ale 10 ccs.
Or pinachrom, 1 : 1000 ale 10 ccs.
Alcohol 333 ccs.
Water 666 ccs.
To make the stock solution of this dye 1 g. should be dissolved in 100 ccs. hot alcohol and 600 ccs. cold alcohol added and 300 ccs. distilled water.
Sensitol Violet, issued by the Ilford Co., England, is a similar dye, and should be, according to the makers, dissolved in the ratio of 1 : 1000 warm alcohol and then diluted with cold alcohol to 5000. For red-sensitive plates the following should be used :
Alcohol 333 ccs.
Stock dye sol 13.5 ccs.
Water 666 ccs.
Time of bathing 3 minutes; dry without washing in current of dry air. It is stated that this bath keeps in good condition and may be strengthened after use. For the best rendering of green at the same time as orange and red, sensitol green should be also used, in the ratio of 1 violet to 2 green. Sensitol violet sensitizes feebly from 5000 to 5200, therefore, this should be the transmission of a safe light for these plates.
C. E. K. Mees and A. Gutekunst91 described the preparation and sensitizing powers of naphthocyanole, acetaminocyanole and kryptocyanin. The first sensitizing for red with a marked gap in the green. The second shows a range to 7600, but only seems suitable for addition to emulsion, and not for bathing in consequence of the hydrolysis of the dye. Kryptocyanin in 1 : 500,000 without ammonia or alcohol sensitizes to 7700, with a very wide gap in the green, and is only suitable for infra-red and astronomical work.
A. and L. Lumiere and H. Barbier92 gave the spectral curves obtainable with cyanin A, prepared from di-methyl-amino-quinolin and iodo-ethyltolu-quinaldin which sensitizes to 6800. And cyanin B, from iodo-ethylate of dimethyl-amino-quinolin and di-methyl-amino-quinaldin, sensitizing to 7000. Also pantochrome prepared like the last but with dimethyl-aminobenzaldehyde, which sensitizes to 7000, but without the marked minimum in the blue-green of the former dye. These dyes differ from the older