Patent GB-204693-A (GB)
Title: Improvements in apparatus for photometric, polarimetric and spectrometric determinations
IPC: G01N21/29
Filed: 1923-09-11
Abstract: 204,693. Jobin, M. L. A., and Yvon, G. G. J. Oct. 2, 1922, [Convention date]. Photometric apparatus.-Comprises an arrangement of apparatus mounted on a common base plate which may be used as a photometer for testing absorption or diffusion or as a polarimeter. Provision is made for the use of monochromatic, ordinary or polarized light. In the majority of the arrangements of the apparatus use is made of a Lummer-Brodhum photometric cube the central portion of the field of which is a reflecting surface, and the outer portions transparent surfaces. The outer portions are illuminated by a direct beam of light and the central portion by a beam at right-angle to the direct beam, which has passed through the material under test. Both beams are parallel when passing through the cube and are observed by a collimating telescope. Fig. 3 shows the apparatus common to the majority of the combinations consisting of a tube 4 containing a collimating lens 6 whereby a parallel beam of light is directed on to a reflecting prism 7 mounted on a support 8 secured to the base board 3. The beam then passes through a Nicol prism 10 mounted in a graduated circle 12 and the trough 20, containing the substance under test, to a second Nicol prism 14 and thence to the reflecting surface of the cube 22 from which it is directed in the same direction as a direct beam of light reaching the cube 22 through the tube 21 containing adjustable neutral glass elements 26. Similar glass elements 15 are mounted at the end of the trough 20. The two beams after passing through the cube 22 are brought to a focus at the diaphragm 31 by the collimating lens 27, and are observed by the eyepiece 37 of the collimating telescope 35 comprising objectives 33, 34 and a diaphragm 36, through the rejecting prism 32. When the apparatus is to be used for the observation of illuminants of the same colour, additional elements shown in Fig. 4 are fitted. In line with the tubes 28, 21 is disposed a tube L41, having a collimation objective L43, which renders parallel a beam of light from a light source outside the tube L41. The illumination of the two parts of the cube 22 is made equal by the variation in the crossing of the Nicol prisms and by the addition of neutral glass elements either at the point 26 in the path of the first beam or at the point 15 in the path of the second beam. Absorption tests are carried out with the addition of a pentagonal prism A44, Fig. 4, and a reflecting prism A45 mounted on an adjustable base 48. This base 48 also carries a receptacle D49 and is rotatable through a right angle on a pivot so that the beam of light either passes through the receptacle and is reflected by the prism or is only received by the receptacle D49, in which position tests of the diffusion may be carried out. The material for absorption tests is contained in the tubes A52 and compared with that in the tube A53. When such tests are on very small quantities of the material the tube A52 is replaced by a microscope device. Polarimetric measurements are made bv removing the prism 7. the neutral screen 15, and the cubs 22 and by replacing the eyepiece 37 by an illuminating device comprising a reflecting prism and a source of light. In place of the cube 22 a reflecting prism is used and an eyepiece is fitted to the graduated circle 12, for observation. Spectrometric measurements are made with the aid of a spectrometer of the constant deflection type placed on the base plate 3 between the telescope 35 and the trough 20 so the light reflected from the prism S71, which is turned into the path of the beam. is received by the spectroscope. Various other arrangements of the apparatus described are indicated in the Specification for carrying out various combined tests.