the chemist kit, like all items with smarts bonus, help boost your smarts skills. For example, with the aid of smarts equipment you are more likely to find pieces of evidence when searching a crime scene.
Or, depending upon what smarts skills you have, it can help you narrow the evidence. For example, if you find a footprint and have footprint analysis, having smarts equipment on will boost you odds of being able to determine whether the footprint is from a heavy or slim person.
When you see a piece of equipment you aren't familiar with, you can get the info on it, such as:
"This portable chemist's kit is helpful when analysing physical evidence found at the crime scene. Smarts Test Adjustment: 2"
So, if you have this with you when you are trying to do something that requires smarts skills, such as search a crime scene, your smarts skills will be counted as two points higher. You might find more evidence, or more specifics on the evidence, depending on your evidence skills.