SCIENCE— ADVERTISEMENTS 



BIOLOGICAL STAINS 



A Complete List for Bacteriology, Pathology, Botany, Zoology, Etc. 

 CHEMICAL INDICATORS 



Indicators for Every Purpose, including the Hydrogen-Ion Indicators 



(Clark Eind Lub's List, Sorensen's List, Etc.) 



FINE ORGANIC CHEMICALS 



Especially Prepared for Laboratory Use 



By specifying Coleman & Bell products, you are assured of receiving chemicals manu- 

 factured under expert supervision and subjected, prior to sale, to the most rigid chemical 

 and biological tests knovirn. The result of our efforts to produce products of the highest 

 quality is shown by the report of Dr. H. J. Conn, Chairman of the Committee on Technic, 

 Society of American Bacteriologists. In the report of the committee upon "An Investiga- 

 tion of American Stains," (J. of Bact., Jan. 1922), it vras stated that the Coleman & Bell 

 stains were entirely satisfactory. In no instance did the product of any other concern 

 surpass a C. & B. stain. In a number of instances, the marked inferiority of the pro- 

 war German product to C. & B's stains was commented upon. 



Write for our Catalogue of Biological Stains, Chemical Indicators and Organic Chemicals. 



Coleman & Bell Products may be secured from Laboratory Supply Houses throughout 

 the United States and in foreign countries, or may be ordered direct. 



THE COLEMAN & BELL COMPANY 



NORWOOD, OHIO, U. S. A. 



THE WAVELENGTH SPECTROMETER has 



become an essential adjunct to the well equipped 

 Laboratory. Its convenience, accuracy and sturdy 

 construction make the Wavelength Spectrometer 

 an ideal instrument for spectrum and color 

 analysis 



GAERTNER SPECTROMETERS embody the 

 results of upward of twenty-five years of experi- 

 ence gained in the construction of precision optical 



instruments. 



Prompt Delivery on Standard Instruments 



Our Specially Designed 

 ULTRAVIOLET AND INFRARED SPEC- 

 TROMETERS 



are useful for many investigations. A very valu- 

 able combination in conjunction with the Wave- 

 length Spectrometer is the improved 



NUTTING PHOTOMETER 



Features: 



1— DESIGN OF THE INSTRUMENT. The de- 

 sign of the instrument provides for greatest 

 rigidity and permanence of adjustment as the 

 composite parts have been reduced to a mini- 

 mum by joining as many as practicable in a 

 single casting, at the same time giving the Spec- 

 trometer a graceful appearance. 



2— ACCURACY IN CALIBRATION. Greatest 

 care is taken in calibrating the wavelength drum 

 in order to insure the highest possible accuracy. 



3— EASY READING OF DRUM. The divisions 

 are sufficiently heavy and distinct and the fig- 

 ures ample and spaced to best advantage. 



4— ESSENTIAL PARTS INCLUDED: 



Protection cap for prism — 



Leveling screws in tripod- 

 Bilateral micrometer slit — 

 Extra high power eyepiece — are fur- 

 nished with the instrument and in- 

 cluded in purchase price. 



LABORATORY APPARATUS 



INSTRUMENTS OF PRECISION 



UNIVERSAL LABORATORY 



SUPPORTS 



Wm. Gaertner & Co. 



5345-49 Lake Park Avenue 

 CHJCAGO, U. S. A. 



