How many letters does the top answer for “a colorless flammable gas used chiefly in welding and in organic synthesis” have?

The most common answer is acetylene (9 letters).

Crossword clue: a colorless flammable gas used chiefly in welding and in organic synthesis

3 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

acetylene 9 letters wn-def

a colorless flammable gas used chiefly in welding and in organic synthesis

alkyne 6 letters wn-def

a colorless flammable gas used chiefly in welding and in organic synthesis

ethyne 6 letters wn-def

a colorless flammable gas used chiefly in welding and in organic synthesis