---------------------+-----------+------+----------+---------+------ Amyl acetate | 0.039 | 0.053| 0.067 | 0.478 | 1.326 Ethyl acetate | 0.686 | 1.224| 2.219 | 4.457 | 6.733 Amyl alcohol | 0.225 | 0.300| 0.442 | 1.581 | 2.167 Butyric acid | 0.009 | 0.021| 0.066 | 0.329 | 0.580 Valeric acid | 0.029 | 0.119| 0.523 | 1.394 | 4.036 Ethyl ether | 5.833 |10.167| 14.944 |17.6667 |60.600 Butyl mercaptan | 0.018 | 0.037| 0.055 | 0.120 | 0.177 Isobutyl mercaptan | 0.008 | 0.018| 0.025 | 0.041 | 0.060 Ethyl mercaptan | 0.046 | 0.088| 0.186 | 0.357 | 0.501 Propyl mercaptan | 0.006 | 0.020| 0.028 | 0.043 | 0.054 Amyl thioether | 0.001 | 0.007| 0.0115 | 0.012 | 0.015 Ethyl thioether | 0.012 | 0.042| 0.107 | 0.223 | 0.271 Allyl isothiocyanate | 0.008 | 0.012| 0.024 | 0.030 | 0.201 Methyl isothiocyanate| 0.015 | 0.039| 0.067 | 0.108 | 0.144 Amyl isovalerate | 0.012 | 0.018| 0.039 | 0.072 | 0.082 Carbon tetrachloride | 4.533 | 9.222| 10.024 |31.333 |38.444 Chloroform | 3.300 | 6.800| 12.733 |28.833 |46.666 Iodoform | 0.018[40] | | | | Artificial musk |0.00004[41]| | | | Nitrobenzene | 0.146 | 0.178| 0.222 | 0.563 | 1.493 Phenyl isocyanide | 0.002 | 0.005| 0.013 | 0.042 | 0.105 Pyridine | 0.032 | 0.146| 0.301 | 2.265 | 5.710 Methyl salicylate | 0.100 | 0.145| 0.179 | 1.526[42]| Oil of peppermint | 0.024 | 0.032| 0.109 | 0.332 | 0.348 ---------------------+-----------+------+----------+---------+------ [Footnote 35: Maximum concentration obtainable.] [Footnote 36: Maximum concentration obtainable.] [Footnote 37: Maximum concentration obtainable.] [Footnote 38: Maximum concentration obtainable.] [Footnote 39: Maximum concentration obtainable.] [Footnote 40: Maximum concentration obtainable.] [Footnote 41: Maximum concentration obtainable.] [Footnote 42: Maximum concentration obtainable.] =Touch Method.= This method consists of dipping a small glass rod drawn to a needle-like end to the depth of 1 mm. in the compound and then quickly touching the skin. The method is qualitative only. [Illustration: FIG. 119.—Skin Irritant Vapor Apparatus.] =Use of Solutions.= Alcohol, kerosene, olive oil, carbon tetrachloride and other solvents may be used for the purpose of determining the lowest effective concentration of a substance, and for the determination of the relative skin irritant efficiencies of various compounds. Since the skin irritants were scarcely ever used in this form in the field, that is, in solution, the method is not as satisfactory as the vapor method. CHAPTER XXII