380 abstracts: spectrophotometry 



are of so delicate a nature that they can only be obtained in a tangible 

 form by a process of maceration with a purified fat, known as enfleurage, 

 whereby the perfume is absorbed and may subsequently be extracted 

 with alcohol. As examples of this class there may be mentioned the 

 flowers of the violet, jasmine, tuberose, jonquil, lily of the valley, and 

 mignonette. 



The various families of plants which have been considered by the 

 author for the purpose of illustration include the Coniferae, Gramineae, 

 Palniae, Liliaceae, Iridaceae, Zin giber aceae, Orchidaceae, Aristolocki- 

 aceae, Annonaceae , Myristicaceae, Lauraceae, Cntciferae, Rosaceae, 

 Geraniaceae, Myrtaceae, Umbelliferae, Ericaceae, Labiatae, and Ccnn- 

 positae. In connection with these groups numerous volatile products 

 have been described with reference to the chemical character of their 

 individual constituents. The preparation by synthetic methods of 

 some of the odorous substances which occur in nature, or of compounds 

 related to them which are largely used in perfumery, has also received 

 consideration. F. B. P. 



SPECTROPHOTOMETRY. — The ultra-violet and visible transmission 

 of eye-protective glasses. K. S. Gibson and H. J. McNichoIvAS. 

 Bur. Stand. Tech. Paper No. 119. Pp. 47. 1919. 



Many glasses are on the market and extensively advertised to pro- 

 tect the eyes from injurious radiant energy. Unfortunately, but little 

 authoritative information concerning the properties of these glasses 

 has been available. The public and even oculists and physicians 

 have had little to guide them in selecting such glasses except the claims 

 of makers and agents. One purpose of such glasses is to absorb the 

 injurious radiant energy which is emitted along with the light from 

 certain lamps, as well as from welding arcs and industrial furnaces, 

 while transmitting sufficient light for vision. They thus act as filters. 

 Another purpose in certain cases may be to absorb part of the light 

 so as to reduce a bUnding brilliance. Glasses of different types are 

 required for different needs. The degree to which these glasses actually 

 fulfill their avowed ptupose can only be determined by measurements 

 of their "transmission" {i. e., the ratio of transmitted energy to the 

 energy falling on them) for the various forms of radiant energy in 

 question. This paper gives the results of such measurements made 

 on a great number of glasses now on the American market. A sug- 

 gested specification for eye-protective glasses is given. K. S. G. 



