Kolbe resulted in the discovery of many new facts and in a better understanding of the relations between the oxyand the amido-acids.
For this purpose the urine is concentrated and the hippuric acid precipitated by the addition of hydrochloric acid; it is then filtered and boiled for some time with concentrated hydrochloric acid, when it is hydrolysed into benzoic and amido-acetic acid.
Chlor-, brom-, iodoand fluor-benzoic acids are known and can be obtained by oxidizing the corresponding halogen toluenes, or from the amido acids, or by substitution.
Freund, Ber., 1895, 28, p. 94 6; 1896, 29, p. 2501), crystallizes in long needles, which melt at 181-183° C. The addition of sodium nitrite to an aqueous solution of its hydrochloride converts it into amido-triaz / N N sulphol S< 1.
Tafel, Ber., 1886, 19, p. 1924), by distilling the amido-acids with lime, by heating phenols with zinc chloride ammonia (V.