This page of our guide to Sherlock Holmes Chapter One describes the minigames, during which you have to investigate the chemicals. The first such minigame will appear in Ghosts of the Past - murder case. This page describes the mechanics of this part of the gameplay, and the walkthrough contains the exact instructions for each mechanic separately.
Start by identifying the necessary reagents. It's easy to check. The elements are marked under the unknown substance. They are marked with colors and corresponding numbers, so they are easy to see.
After finding the right substances, place them on the board on the left. It is best to stack them vertically, one under the other. This will make it easy to connect them later.
The next step is to get Chemical Operations on the board. Then hover over the necessary substances and drag them to Chemical Operations. You will do this with the right mouse button. This way, they will be connected with thin lines. You will be able to continue the test.
The final step is to connect everything to the unknown substance. This will give you the test result.
Pay attention to the reagents. In some situations, you will have to connect Chemical Operations with each other, and one of them with an unknown substance, in order to get the correct result. Our walkthrough describes all the chemical tests that need to be done in the game.