Molecular Weight

A weight of the smallest particle that can exist. Molecular weight is ascertained by adding together the weights of all the atoms of the various elements, which have united to form the molecule of the chemical.


The smallest quantity of two or more atoms forming a chemical compound.


A picture in one color.


An uneven appearance, usually apparent in the negative which has been developed in a solution that was not sufficiently agitated.

Mount and Mounting

A cardboard or other support to which the photographic print is attached.


A viscous substance or adhesive used for mounting prints.

Double Mounting

Double mounting is the placing of a print on a secondary mount, which latter is attached to the real mount or base. The secondary mount should be of a different shade, yet of the same color, as the base.

Dry Mounting

A process of mounting prints by means of a specially prepared tissue. A very convenient method of securely fastening prints on flexible mounts.

Lens Mounting

The brass or aluminum body to which the lens cells are attached.

Multiple Mounting

Multiple mounting calls for the use of more than two tints of paper or light cardboard on which to place the print. Each successive layer underneath the print is a trifle larger than the preceding one. The photographer's taste and skill are brought into play when using this method of mounting, as it is by the artistic combination of various tints and shades that the value of the picture will be enhanced, rather than detracted from.

Dry Mounting Tissue

A specially prepared tissue used for dry mounting. Mounts, Sizes of.

Petite Cards

1 5/8x3 1/8.

Carte-de-visite - 2 1/2 x 4 1/8. Cabinet - 3 7/8 x 5 1/2. Paris Panel - 7 1/2 x 13.


A term given to various forms of adhesives composed of gums, dextrine, etc.

Multiple Mounting

(See Mounting Multiple.)

Muriate of Ammonia

(See Ammonium Chloride.)

Muriate of Lime

(See Calcium Chloride.)

Muriate of Platinum

(See Platinum Chloride


Muriatic Acid

(See Acid Hydrochloric.)


Benzin; Petroleum Ether. Light, transparent, colorless, volatile liquid. Soluble in ether, oils and carbon disulphide. Used extensively in dissolving various resins, also in the manufacture of varnishes.

Naphtha, Coal. (See Benzene.)

Mineral Naphtha

Mineral Naphtha is another name for petroleum oil or kerosene. Use: It is a solvent for India rubber, sulphur, phosphorous, camphor, iodine and a large majority of the resins, wax, fats, etc. It is also employed for illuminating purposes. Mixes with alcohol and oils, but not with water.

Wood Naphtha

A name given to impure methylic alcohol. Naphthol, Green.

Green powder. Soluble in water, giving a yellowish-green color. Used in color photography.