258 Harriny—TZhe Action of Heat on the Absorption Spectra and 
JRIY I, 
The Absorption Spectra described. 
The spectra of metallic solutions are principally of three kinds :— 
(1) Continuous spectru, or bands of rays uninterruptedly transmitted. 
(2) Groups of rays of different refrangibilities separated by one or more broad 
absorption bands. 
(3) Spectra interrupted by sharp black bands or lines. 
Substances showing such spectra as the second—for instance, chromium salts 
—are markedly dichroic. I propose to take the simplest spectra first. 
The Spectra of hot and cold Solutions of Copper and Nickel Salts —A continuous 
absorption in the red, or in both red and blue, characterises these substances, and 
_they are therefore generally green or blue in colour. 
The Spectra of Nickel Salts. (Plate XVII.) 
Aqueous Solutions. ~ Temperature. | Rays transmitted. REMARKS. 
Nic9H,0, . . .| 20° | 6i8to4o1 Bes Ceres 
99 29 : 100° 598 — 507 — 
NiSO,7H,0, ‘ : ; 18° 588 — 464 Bluish green. 
5 Ap : : 100° 588 — 4438 Yellowish green. 
Ni(NO;).°6H,0, . ; , 18° 557 — 462 Green solution. 
Po ts iver 100° 560 — 464 = 
NiSO,K,80,6H,0, : ; 20° 689 — 467 — 
- a 3 100° 689 — 491 x 
NiSO,(NH,).SO,°6H,0, : 16° 659 — 438 — 
' . - 100° 655 — 446 _ 
NiBr,'6H,0, : : ; 16° 635 — 602 A brown solution, almost opaque. 
- » 100° at 633 only. = 
Nil,-7H,0, . : ; ‘ 16° 643 — 466 A brown solution, almost opaque. 
- es ; : 100° 633 — 486 Thin wedge-cell. 
Nickel acetate, . : é 20° 657 — 472 Thick wedge-cell. 
° ” 100° 662 — 482 = 
Potassio-nickel oxalate, : 20° 689 — 425 — 
5 ean 100° 689 — 491 = 
Ammonio-nickel oxalate, : 16° 659 — 438 — 
J f > 100° 655 — 446 = 
