| CO | A heavy odorless colorless gas formed during respiration and by the decomposition of organic substan |
| PROVE | Ascertain / substan tiate |
| COAL | Black or brown combustible mineral formed by decomposition of organic matter and used as fuel |
| BREATH | Intake of oxygen and expulsion of carbon dioxide during respiration; one such inhalation or exhalation; a sound so produced; or, life itself (6) |
| PUTREFACTION | Decomposition of organic matter, especially protein, by micro-organisms (12) |
| HUMUS | Organic component of soil, formed by the decomposition of plant and animal matter (5) |
| METHANE | A greenhouse gas emitted by the decomposition of landfill waste (7) |
| KAOLIN | Fine white clay produced by the decomposition of feldspar and other minerals, used to make porcelain and bone china (6) |
| HUMIC | Of, or relating to, natural organic compounds in the soil, formed from the decomposition of plant and animal residues (5) |
| ELECTROLYSIS | The decomposition of a substance by the application of an electric current |
| FIREDAMP | Mixture of gases, chiefly methane, which occurs from the decomposition of coal (8) |
| FOAM | A mass of small bubbles of gas formed on the surface of a liquid (4) |
| CAPITALOFZAIRE | Z (By the way, I made this puzzle in mid-May 1997 when the country was still called this, and by the time the puzzle came out in newspapers just two weeks later, the country's name had been changed. |
| SCHWITTERS | Artist who fled Nazi Germany to the Lake District where he sought both refuge and refuse by means of peace and by the found objects or rubbish for his "Merz" collages (10) |
| GAS | It's sold by the gallon in the U.S. and by the liter in Europe |
| NODDING | "When you are old and grey and full of sleep / And ... by the fire" (Yeats) |
| YMCA | Disco classic spelled out with arm motions and by the ends of the answers to the starred clues |
| SAINTOMER | Alice Diop film inspired by a real French court case and by the story of Medea |
| AIRSAC | Membranous extension of a bird's lung cavity, aiding respiration and decreasing bone mass (3,3) |
| IRONLUNG | A rigid case once fitted over a patient's body to aid artificial respiration and combat polio (4,4) |
