Set of KBr and NaCl prisms for spectroscopy, vintage, new, original boxes

Description

The set consists of 2 (two) vintage prisms for spectroscopic device, one for mid-infrared (MIR) made of potassium bromide (KBr), the other one for ultraviolet (UV), made of sodium chloride (NaCl). Vintage, made in 60's in former East Germany. Both materials are hygroscopic,
so the prisms and their metallic holders are in turn mounted in
a metallic cylindrical protective box with a sealed cap (pictures #1 - #6). Only the metallic protective box for KBr prism was opened, to take pictures (#7 - #9). However its holder with the actual prism was never taken out of its metallic protective box (see the security thread, pictures #7 -#9). The KBr
has a transmittance
better than 80 % between 0.26 - 23 micrometers. The KBr prism is an isosceles triangle prism, the two equal sides are polished, active surfaces (see a reflection in picture #8) and the third surface (base of the triangle) is ground (picture #9). Approximate lengths of the triangle sides: 60 mm x 60 mm x 68 mm (2.35" x 2.35" x 2.68"). Approximate height of the prism: 60 mm (2.35"). The prism's apex angle is approximately 69 degrees. The NaCl has a transmittance better than 80 % between 0.23 - 12 micrometers. Although the protective box for NaCl prism was never opened (see the seal, picture #6), its size should be close to the size of the KBr prism because the refractive indices of the two materials (NaCl and KBr) are close to each other. Originally, both prisms belonged as spectral accessories of the monochromator type SPM2, made by Carl Zeiss, Jena. They can be adapted, however, to other existing spectral devices. Their best use is for professional or educational laboratories, or as vintage, collectible items.