ACTION OF LIGHT.

659

cask, as they phrase it—than that ground in the daylight. The latter findsits way largely to the garancin manufacturers. An investigation on thechanges which madder undergoes while in the cask was commenced someyears ago. Samples were taken out of the casks with a suitable tool everyten days for two years, care being taken to have the casks (about 400 innumber, each containing 750 kilos., and among them 100 containing madderground by daylight) kept in a dark warehouse where the temperature,hygroscopic condition of the air, and the general state of the weather weretaken into account. The series of experiments was unavoidably interrupted,but it was ascertained that there is good reason for preferring the madderground in the dark.

The following table has been drawn up by F. V. Kallab. The samples wereexposed to the sun during the months of July, August, and September, 1872.and were compared with corresponding samples carefully preserved from theaCtion of light:—

Influence of Sunlight.

Dye-ware.

Indigo blue.

Copperas vat on cotton.Vat blue on woollens.ExtraCt of indigo.Purple extract.

Prussian blue.

Logwood blue.

Aniline blue (?)

Nicholson blue.

Weld yellow.Quercitron.

Flavin yellow.

Berries, yellow.

„ orange.

Fustic yellow.

Young fustic orange.

Turmeric yellow.

Picric yellow.

Blackley orange.

Campo-bello yellow.Buff (iron).

Chrome yellow andorange.

From three to eight days.No change.

J1 JJ

»1 »)

Paler.

Rather paler.

Paler by day; recovers itsformer shade by night.

Paler.

Much paler.

Little change.

JJ U

Unchanged.

Paler.

Duller.

Dirty orange.

Paler.

Much paler.

Light shades, whitish.Dark ditto, straw.Orange.

No change.

Three months.

Much lighter.Greenish.

Pure blue but lighter.Very pale and greenish,Less bloomy and paler.If rinsed in water inthe evening the lostcolour does not re-return.

Grey ; lilac shadesnearly white.

Very pale; light shadeswhite.

Paler and duller.Greyer.

Rather paler.

Straw colour.

Nearly white.

Dirty yellow.

Pale dirty orange.Dirty straw.

)> JJ

Quite white.

Reddish.

Like dark young fusticyellow.

Turns a little paler atlast.

Pale reddish at last.No change.

Duller; greenish.

2 u 2