This composition was never called a Nocturne by Chopin. It was probably written in 1830 when he was 20 years old, for his sister Louise, and was marked simply Lento, con gran espressione.
It cannot be said to be in the form of a Nocturne, as Nocturnes are not written in any definite form, but the content justifies the name. It is interesting not only for itself but because it was one of Chopin's first attempts to write the kind of composition for which he afterward became famous.
Edited and with a foreword by Francis L. York.