Value of the ruble in year 1825
This website (in Russian) states that, in 1825,
you could sell 1 Imperial Ruble and get 0.72 US dollars. I don't know Russian so I cannot tell the source of that data. 

Those 0.72 US dollars in 1825 are worth US$15.49 in 2016, according to this website. 

Therefore, 1 Imperial Ruble of 1825 was equivalent to US$15.59 in 2016.

Additionally, this website has information of prices of different goods and wages for Russia since the 16th century.