A saccharimeter is an instrument for measuring the concentration of sugar in a solution. 
La maison Soleil, fondée en 1819 par Jean-Baptiste Soleil, est reprise en 1849 par son fils Henri et par son gendre et apprenti Louis Jules Duboscq (1817-1886), fils d’un cordonnier de Villaines-sous-Bois (Val d’Oise). 
In  1870 he invented a colorimeter. Colorimeters are used to determine concentrations of substances by measuring color intensities. The Duboscq type of colorimeter works by comparing the colors of two solutions of a colored substance, a standard with a known concentration, and a sample with an unknown concentration.
H.16 in x L.20 , a couple of pieces are missing , a ruler and a tube , overall seem complete