USEFUL ALGAE — CHASE 445 



ALGAE AND PHOTOGRAPHY 



In 1882 Mitchell proposed the substitution of agar for gelatin in 

 the preparation of photographic materials needed in tropical coun- 

 tries. Several patents were obtained for this purpose. Manipulative 

 difficulties and inconsistent results prevented photographic manu- 

 facturers from placing agar products on the market to any great 

 extent, although a few firms in Germany and England were manu- 

 facturing agar papers some years ago. Cooper and Nuttall experi- 

 mented further on the application of agar to photography. An agar 

 film need be but one-eighth as thick as a gelatin film. Other ad- 

 vantages are that agar as compared with gelatin is cheaper and is 

 more insoluble in water except when it is very hot. One firm states 

 that as a reagent in sensitized emulsions, agar has proved to be of 

 better quality than any similar material now on the market. In 

 photomechanics the term "colloid" is applied to all substances that 

 are capable of being rendered insoluble in water when impregnated 

 with bichromates and exposed to the action of light. For this reason, 

 agar and Irish moss are among the colloidal materials that are of 

 value in the various phases of photomechanical plate making for 

 the production of photographic images. 



ALGAE AND WAR MATERIALS 



During World War I, the Germans made a surprising use of 

 a variety of Laminaria. When dry, the kelps with their massive 

 thalli diminish in volume and become wrinkled. As soon as they 

 are placed in water, they absorb the water, swell up, and return to 

 their natural form. Some of the German grenades that fell into 

 bodies of water or humid places, exploded after a certain length of 

 time. When similar grenades were studied, they were found to 

 contain sulfuric acid in a small glass ampoule and potassium chlorate. 

 The grenades were hermetically closed with a piece of Laminaria 

 cloustonii bearing at its internal end a sharp metallic point. With 

 humidity the piece of seaweed elongated so that it pushed the metallic 

 point against the ampoule, thus breaking it. The contact of the 

 released acid and the chlorate caused an explosion. In other grenades 

 the needle pushed by the piece of seaweed came in contact with a 

 capsule of fulminate. 



Algin is used as a binder in cartridge primers here in the United 

 States. 



ALGAE AND OTHER INDUSTRIES 



In connection with national defense work, the algin products made 

 by a company on the Pacific coast are supplementing the foreign 

 gums such as tragacanth, locust bean, gum arable, and other gums 

 which are practically nonavailable since the present war started. 



