BAIRD &TATLOCK. (LONDON) LTD. 



A-B. 



5016 5017 



)16 5 Kunkler's Viscometer, for testing the viscosity of fats, greases, etc., especially suitable 

 for small samples, and for cylinder oils at 150 C. . . 



)17 S Viscometer, Coleman-Archbutt's. Complete on stand, with burner, thermometer, etc. 

 This instrument is an improved form of the well-known viscometer first used by Coleman about 1869. It 

 nsists of a glass pipette contained in an outer water-jacket, with a funnel for pouring in hot or cold water, a 

 be for running off water, and a stirrer for thoroughly mixing the water in the jacket. The neck at the lower 

 il of the jacket is made narrow, a rubber stopper not more than -fa in. thick is fixed in it, and the jet of the 

 lux tube projects through the stopper only fa in., and does not extend quite to the end of the neck. Thus 

 e oil in the tube is surrounded by the water in the jacket until it has reached nearly to the end of the jet, and 

 e temperature is maintained constant until the oil has passed out of the tube. The jet is protected from change 

 temperature as well as from fracture by being contained entirely within the neck of the jacket. The efflux tube 

 narrowed for a short distance above the jet, and four circumferential marks are etched upon it. The lowest 

 zero mark is rather above the middle of the narrow portion ; the other three marks are on the wide portion and 

 vide the tube above the zero mark into capacities of 25 cubic centimetres, 50 cubic centimetres, and 100 cubic 

 ntimetres. The volume of oil used for a test may therefore be varied according to the viscosity and the quantity 

 ailable. But the tube must be separately standarised from each mark, as the times of efflux of the different 

 >lumes bear no simple relation to each other. The temperature is maintained constant by pouring hot or cold 

 iter into the jacket, through the funnel, and running off the excess as often as required, using the stirrer 

 ^quently. The temperature is indicated by a thermometer immersed in the water. The oil, having been brought 

 about the desired temperature, is poured into the efflux tube, where the final adjustment is made by stirring 

 th a thermometer, which is removed before the oil is run out. The jet is closed by a plug of soft wood, which 

 now removed and replaced by the finger, and the level of the oil is adjusted exactly to the mark which it is 

 sired to run it from. It is then allowed to flow out, and the time occupied in reaching the zero mark is measured 

 a stop watch, and compared with the time occupied by the standard oil to flow out under exactly similar 

 cumstanccs. When it is desired to make a determination at 212 F., the temperature of the water is gradually 

 iscd to about 180 F. by pouring in very hot water, and then the funnel is removed and replaced by a tube 

 nnected with the metal boiler, and steam is blown in until the water boils. A short bent glass tube is provided 

 ." the escape of steam. The length of the jet is about I in., and the diameter is such that 100 cubic centimetres 

 re rape oil at 60 F. takes about ten minutes to flow out. 



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CHEMICAL AND SCIENTIFIC APPARATUS AND PURE CHEMICALS. 



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