Throughout this original and moving memoir, the consistent theme that repeatedly shines out is the way in which chemistry is compared to real life. Levi constructs many links between these two aspects, and the title draws attention to the way in which this novel makes comparisons and gives scientific accounts of a variety of experiences and substances. Consider, for example, the way that the novel starts and how inert gases are linked to the life of the author:

They are indeed so inert, so satisfied with their condition, that they do not interfere in any chemical reaction, do not combine with any other element, and for precisely this reason have gone undetected for centuries.

As we read, we realise that this description forges a link between inert gases and his own family's inert nature in the face of increasing evidence of the plans of Germany for the Jews. In "Potassium," Levi comments on the inert state that his family willingly embraced in order to ignore the evidence and news that was arriving from different countries: "We pushed all dangers into the limbo of things not perceived or immediately forgotten.”

Levi comments on the similarities between his career as a chemist and what happened to the Jews. For somebody who has spent his life analysing the impurities of elements, it is a grim irony that Levi and his people are treated like an impure element. This allows him to discuss the various impurities in human beings.

Chemistry is therefore presented in this novel as an exciting medium to enable Levi to delve into the nature of humanity, and chemistry consistently points towards the chemical mystery of human life, the random collection of cells that forms us as individuals, or, as Levi puts it, "the me who is writing." The novel ends also by focusing on the power of the human will and its ability to assert itself, as Levi describes how he is doing this in his writing by focusing on "this dot, here, this one," which suggests that Levi has used chemistry to describe as much of his life as he is able to.