Did Raff ever change this dedication?
AFAIK it was always dedicated to the Belgian violinist Hubert Léonard, an enthusiast for Raff's music. Why do you ask, Eric?
The edition of the sonata published (posthumously) by Peters bears a dedication to Ferdinand Laub, which is confusing to me. Thanks!
Raff dedicated his First Violin Sonata (1853) and Fourth String Quartet (1867) to Laub, a German violin virtuoso. To dedicate a third work to him in the following year seems most unlikely. I think that Peters just made a mistake. The Violin Sonata was re-published by them in 1891 (it was originally published by Schuberth in 1869), and I have scans of two title pages of the their edition: one with Laub as dedicatee and the other with Léonard. The title page designs of all five Sonatas in the Peters editions are identical barring the work title and the dedicatee, and Laub was the dedicatee of the First Sonata. I suspect that they didn't change that when the prepared the plate for the Fifth, issued some like that, realised their mistake, corrected the title page plate and printed the rest from that. Below is a scan of the Peters edition showing Léonard as dedicatee (compare this with the otherwise identical copy available form IMSLP showing Laub as dedicatee):
(http://www.raff.org/otherpix/Violin_Sonata_No.5.png)
ah, thank you. Added a paraphrased explanation on the discussion page @ IMSLP. :)
(the copy I see @ IMSLP has Laub, but maybe there's another copy @ IMSLP I'm missing...)