As a means of overcoming the difficulty of structure, the beans were allowed to stand in water in order to swell, or the cells were expanded by treatment with steam, or the beans were subjected to the action of some "cellulose-softening acids," such as acetic acid or sulphur dioxid. As a method of facilitating the mechanical side of extraction without deleterious effects, the treatment of the coffee with steam under pressure, as utilized in the patented process of Myer, Roselius, and Wimmer,[141] is probably the safest. Many ingenious methods have been devised for the ready removal of the caffein from this point on. Several processes employ an alkali, such as ammonium hydroxid, to free the caffein from the acid; or an acid, such as acetic, hydrochloric, or sulphurous, is used to form a more soluble salt of caffein. Other procedures effect the dissociation of the caffein-acid salt by dampening or immersion in a liquid and subjecting the mass to the action of an electric current. The caffein is usually extracted from the beans by benzol or chloroform, but a variety of solvents may be employed, such as petrolic ether, water, alcohol, carbon tetrachloride, ethylene chloride, acetone, ethyl ether, or mixtures or emulsions of these. After extraction, the beans may be steam distilled to remove and to recover any residual traces of solvent, and then dried and roasted. It is said[142] that by heating the beans before bringing them into contact with steam, not only is an economy of steam effected, but the quality of the resultant product is improved. One clever but expensive method[143] of preparing caffein-free coffee consists in heating the beans under pressure, with some substance, such as sodium salicylate, with the resultant formation of a more soluble and more easily steam-distillable compound of caffein. The beans are then steam distilled to remove the caffein, dried, and roasted. Another process of peculiar interest is that of Hubner,[144] in which the coffee beans are well washed and then spread in layers and kept covered with water at 15 deg. C. until limited germination has taken place, whereupon the beans are removed and the caffein extracted with water at 50 deg. C. It is claimed by the inventor that sprouting serves to remove some of the caffein, but it is quite probable that the process does nothing more than accomplish simple aqueous extraction.