Question

In specific gravity test the following observations were made
Weight of dry soil : 50 N
Weight of bottle + soil + water : 100 N
Weight of bottle + water : 85.5 N

If while obtaining the weight 100 N, 3 ml air remained entrapped in suspension, then the percentage error obtained in measuring the specific gravity of soil solids is

• A. 0.08%
• B. 0.06%
• C. 0.04%
• D. 0.03%

Answer 1

The correct option is A 0.08%

$G=\frac{W_2-W_1}{(W_2-W_1)-(W_3-W_4)}=\frac{50}{50-(100-85.5)}$

$G=1.4085$

If some air is entrapped while the weight $W_3$ is taken, the observed value of $W_3$ will be lower than if water is occupied by air space.

$W_3^{\prime }=100+0.03=100.03$

$CorrectG=\frac{50}{50-(100.03-85.5)}$
$G=1.4096$

$Percentageerror=\frac{1.4096-1.4085}{1.4096}\times 100=0.08\%$