/**
* Compound needed to reach a target concentration for an element.
*
* In case no element is specified the default proxy element for the
* compound is used.
*
* @param Concentration $target Target concentration.
* @param CompoundInterface $compound Compound to be added.
* @param string|null $element Element used for target.
*
* @throws ImpossibleCalculation When the target concentration is impossible.
*
* @return float Times the compound should be added to reach the target.
*/
public function targetElement(Concentration $target, CompoundInterface $compound, $element = null)
{
if ($target->toUnit() * $compound->getVolume()->toUnit() >= $compound->element($element)->toUnit()) {
throw new ImpossibleCalculation();
}
return $target->toUnit() * $this->volume->toUnit() / ($compound->element($element)->toUnit() - $target->toUnit() * $compound->getVolume()->toUnit());
}
public function testToString()
{
$concentration = new Concentration(3.0E-6);
$this->assertEquals('3ppm', $concentration->__toString());
}
