10% Solution

A ten-per-cent solution is made by dissolving one part of a substance in ten parts water.

Spatula

An instrument similar to a knife, having a thin blade with a round end, used for mixing chemicals in the form of a paste.

Specific Gravity

The ratio of the weight of a given bulk of any substance to that of a standard substance. The substance taken as the standard is water for solids and liquids, air or hydrogen for gases. The weights of bodies being proportional to their masses, it follows that the specific gravity of a body is equivalent to its relative density, and the term DENSITY has nearly displaced specific gravity in scientific works. As long as the term specific gravity was in use, water at 62 ° Fahr, was taken as the standard in England; when the term density is used, water at its maximum density 4o Cent. or 39.2° Fahr. - is the standard. A common method of obtaining the specific gravity of solids is to weigh the body in air, then in pure distilled water, and divide the weight in air by the loss of weight in water, the result being the specific gravity of the body. - (Century Dictionary.)

Specific Heat

The number of heat units, or in other words, the amount of heat required to raise equal weights of different substances through one degree of temperature. Water is taken as the standard. The definition given by Clerk Maxwell is, the specific heat of a body is the ratio of the quantity of heat required to raise that body 1° to the quantity required to raise an equal weight of water 1°.

Spectroscope

An instrument employed to separate the rays of light in order to find the spectrum.

Spectrum

A band of light showing the component rays of white light. (See Prismatic Colors.)

Spherical Aberration

(See Aberration, Spherical.)

Spenoxylic Acid

(See Acid Salicylic.)

Spirits of Salt

(See Acid Hydrochloric.)

Rust Spots

(See Rust Spots.)

Squeegee

There are two forms of squeegees in photography, one being known as a flat squeegee, the other a roller squeegee. The former is a strip of heavy rubber fastened to a flat wooden handle, while the latter is a wooden roller covered with rubber. The flat squeegee is used principally in the carbon process for expelling water. The roller squeegee is preferred for mounting prints, rolling them in contact with the mount.

Stains

There are many kinds of stains, due to many different causes, but usually they are due to carelessness on the part of the photographer. Various methods for removing stains are given in Volume II, as referred to above.

Stamp Photographs

Small photographs, usually having an ornamental, perforated border, and gummed on the back resembling an ordinary stamp.

Stand Development

(See Tank Development.)

Starch

Usually made from corn, arrow-root, rice and wheat. Used principally in photography for making paste for mounting purposes; it is also a reagent for iodine, the iodine of starch test solution being used to ascertain whether or not hypo is present in a solution. (See Sodium Hyposulphite, Test for Presence of.)