useful in addition to being a very good solvent acetone was found to be nontoxic at concentrations of 4 or lower because of this it was the solvent of choice for the majority of the substrates both ethanol which was found to be nontoxic at 4 and hexane which was found to be nontoxic at 2 were found to be suitable solvents chloroform was not an acceptable solvent since it was found to be lethal at concentrations greater than 1 and it precipitated various components of the broth at these concentrations growth of c tropicalis strain h5343 was measured by absorbance at 600 nm this experiment examined the toxicity of test substrates the data collected from example 1 was used to help prepare a stock solution of the test substrate in one of the solvents stock solutions of most substrates in concentrations from 100 g l to 500 g l were made using acetone as a solvent aqueous solutions of polyethylene glycol were prepared in the few cases that the substrate could not be dissolved in any of the tested solvents it was added neat the toxicity test used here was similar to that used for the solvents described in example 1 the goal was to determine the highest concentration at which a substrate could be added to.