The calculation of percentage solutions is often a puzzle to young assistants and as there are many new ones being broken in at the present time, a word of explanation may not be amiss. See that your assistants read this and similar matter as it appears in the various photographic magazines.

The difficulty about percentage solutions will disappear if the worker will always bear in mind that one fluid ounce of water weighs 437 1/2 grains which is, of course, equivalent in weight to one ounce avoirdupois. It follows that if one-tenth that number of grains - i.e., 43.75 grains - of any ordinary soluble chemical is put into a graduated glass and water added to make up one fluid ounce, the result will be a 10% solution.

In the following table the figures are worked out for solutions of various strengths. If the number of grains indicated in the table are taken and sufficient water added to make up one fluid ounce, it will be found that the solution has the required strength.

For a

1%

solution

take

4.37

grains

''

5%

''

''

21.87

''

''

10%

''

''

43.75

''

''

20%

''

''

87.50

''

''

30%

''

''

131.25

''

''

40%

''

''

175.00

''

''

50%

''

''

218.75

''

Percentage Solutions StudioLightMagazine1918 136

That picture you are going to send him. He will wear it next his heart, it means that much.

Make the appointment to-day.

THE PYRO STUDIO

Line cut No. 253. Price, 50 cents.

Percentage Solutions StudioLightMagazine1918 137

The illustration shows a pamphlet signed by the Association of German Amateur Photographers' Societies and dated Berlin, October, 1917. It is reproduced from a photographic copy lately received in this country. The translation in full is given on opposite page.

If it isn't an Eastman it isn't a Kodak!

A translation of the circular in full is as follows:

"It is the duty of every German to use only German products and to patronize thereby German industry. Therefore, use for photographic purposes only German cameras, German Dry Plates and German papers. Whoever purchases the products of enemy industries strengthens the economic power of our enemies.

"Germans! Remember for all times to come that with the aid of your patronage the American-English Kodak Co. subscribed before the war with the United States, the round sum of 50,000,000 marks of war loans of our enemies!

"There are no German 'Kodaks'. ('Kodak' as a collective noun for photographic products is misleading and indicates only the products of the Eastman Kodak Co.) Whoever speaks of a 'Kodak' and means thereby only a photographic camera, does not bear in mind that with the spreading of this word, he does harm to the German industry in favor of the American-English."

If it isn't an Eastman it isn't a Kodak!

EASTMAN KODAK COMPANY

Rochester, N. Y. The Kodak City

Percentage Solutions StudioLightMagazine1918 138

ARTURA PRINT FROM SEED PLATE NEGATIVE

By Geisler & Andrews New York, N. Y.

STUDIO LIGHT INCORPORATING THE ARISTO EAGLE ESTABLISHED 1901 THE ARTURA BULLETIN ESTABLISHED 1906 Vol. 10 AUGUST 1918 No. 6