Mayim aharonim pure silver

Sages said that it is obligatory to wash hands before blessing the food at the end of the meal,
This washing is called 'last water'.
The purpose of the washing, because they used Sodom salt which could blind the eyes 
 They also said that there is a mitzvah to wash hands before blessing the food.
In order to sanctify oneself for the blessing, it is not appropriate to say the food blessing when the hands are dirty from the remains of the food.
Although it is obligatory to use 'last water', there is no blessing for this washing, since the main purpose of the installation is to prevent danger, and there is no blessing for removing danger.