Co-crystallized acetylenic compounds

A process for producing a co-crystallized composition of at least two different acetylenic compounds, each containing at least one --C.tbd.C--C.tbd.C-- group and substituents selected from the group consisting of sulfonate, urethane and alcohol radicals, at least one of said compounds being capable of undergoing a contrasting color change upon exposure to ultraviolet radiation, gamma radiation, or electron beam, or to thermal annealing;

• which composition exhibits a substantially different thermogram than the sum of the thermograms of the individual components as obtained by differential scanning calorimetry;
• said process consisting essentially of forming a solution of said different acetylenic compounds and recovering said co-crystallized composition from the solution by rapidly and substantially decreasing the solubility of said composition in the solution to thereby obtain co-crystallization before crystallization of the acetylenic compounds separately, by using a means of the groups consisting of (a) fast removal of solvent and (b) rapid mixing of the solution with about 1 to 10 parts, per part of solvent, of a liquid which is miscible with the solvent but is a non-solvent for the co-crystallized composition.