/**
* 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 testConversions()
{
$concentration = new Concentration(1, 'g/l');
$this->assertEquals(1000.0, $concentration->toUnit('mg/l'));
$this->assertEquals(0.001, $concentration->toUnit('g/ml'));
$this->assertEquals(1000.0, $concentration->toUnit('ppm'));
$concentration = new Concentration(1, 'mg/l');
$this->assertEquals(0.001, $concentration->toUnit('g/l'));
$this->assertEquals(1.0E-6, $concentration->toUnit('g/ml'));
$this->assertEquals(1, $concentration->toUnit('ppm'));
$concentration = new Concentration(1, 'ppm');
$this->assertEquals(1, $concentration->toUnit('mg/l'));
$this->assertEquals(1.0E-6, $concentration->toUnit('g/ml'));
$this->assertEquals(0.001, $concentration->toUnit('g/l'));
}
