| 摘要 |
Precipitation of polyacetylenic agents can be effected with control of a particle size parameter such as mean size or spread, by mixing a warm solution of the acetylenic agent with a cold precipitation fluid and appropriate selection of a constituent of the cold precipitation fluid and/or of the temperature conditions and collecting the precipitated acetylenic agent. Precipitation additives such as nitrocellulose or gelatin can usefully be employed. Solvents such as aqueous methanol and ethyl 3-ethoxypropionate can be useful. Polyacetylenic agents, e.g. substituted diacetylenics are useful to provide visual changes in condition-monitoring indicators such as time-temperature indicators, "TTIs", useful as freshness indicators for radiation exposure monitoring and for other purposes. Controlled, small and/or consistent particle sizes of such polyacetylenic agents are helpful in providing consistent commercial properties, especially in inks in which they may be formulated.
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