TABLE A1.

Determination of culture mass density^a

Relative concnb (C)	Observed ODc (Oo)	Calculated ODd (Oc)	Deviation (%)e [(Oc − Oo)/Oo]	Mass densityf (M)
0.0	0.000	0.000	0.0	0.000
0.2	0.184	0.186	0.9	0.191
0.4	0.361	0.360	−0.1	0.382
0.6	0.530	0.524	−1.1	0.574
0.8	0.681	0.677	−0.6	0.765
1.0	0.812	0.819	0.9	0.956

^aA culture of E. coli B/r was grown in glucose minimal medium to an OD₄₆₀ of 0.812, when 200 μg of chloramphenicol per ml was added and the culture was chilled to stop growth. 

^bDifferent mass densities were obtained by adding 1, 2, 3, or 4 ml of culture to 4, 3, 2, or 1 ml, respectively, of growth medium for relative concentrations (C) of 0.2 to 0.8. 

^cThe OD₄₆₀ of the culture dilutions was determined (1-cm light path; observed OD, O_o). 

^dThe OD₄₆₀ of the culture was calculated (O_c) from C, by equations 7 and 8 with a = 0.956 and b = 0.15 (best-fit method). 

^eThe difference calculated minus observed OD, expressed as a percentage. With a = 0.956 and b = 0.15, both the individual deviations and their sum were minimized (sum = −0.1%). 

^fThe mass density (M = corrected OD) was calculated from the observed OD for the different dilutions, by equation 9 with b = 0.15. The calculated values fall on the straight line labeled M in Fig. A1.