2.58: Exercise 15.4
- Page ID
- 94513
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Answer
approximately 9 x 106 cells/mL
Solution
- Find the number corresponding to the absorbance on the graph's axis (in this case 0.04 on the x-axis).
- On the graph, draw a straight line along the absorbance reading on the axis until it reaches the standard line. In this case, draw straight up from 0.04 until it hits the dotted standard line.
- On the graph, draw a straight line from the point identified in step 2. to the other axis (in this case away toward the y-axis).
- Where you intersect the other axis, determine the value of this point on the graph. This will be the approximate CFU at this absorbance. At 0.04 absorbance, the standard line is about at about 9, but the unit given on the graph indicates these numbers should be multiplied by 106. This is how 9 x 106 cells/mL was determined as the CFU at this absorbance.