BAIRD &TATLOCK (LONDON) LTD. 



Short cylinders, d, of either copper, iron, or platinum are supplied with the pyrometer, which are so adjusted that their 

 heat capacity at ordinary temperature is equal to one-fiftieth part of that of the copper vessel filled with one pint of water. How- 

 ever, as the specific heat of metals increases with the temperature, allowance is made on the brass sliding scales, which are divided 

 according to the metal used for the pyrometer cylinders, d. It will therefore be understood that a different sliding scale is required 

 for each kind of metal. In order to obtain accurate measurements, each sliding scale should only be used in conjunction with 

 its own thermometer, and in case the latter breaks, a new scale must be made and graduated for the new thermometer. 



The water pyrometer is to be used as follows : 



Exactly one pint (0.568 litre) of clean water, preferably distilled or rain water, is poured into the copper vessel, and the pyro- 

 meter is left for a few minutes to allow the thermometer to attain the temperature of the water. 



The brass scale c is then set with its pointer opposite the temperature of the water as shown by the thermometer. Meanwhile 

 one of the metal cylinders has been exposed to the high temperature which is to be measured ; and after allowing sufficient time 

 for it to acquire that temperature, it is rapidly removed and dropped into the pyrometer vessel without splashing any of the water 

 out. 



The temperature of the water will now rise, and after an interval the mercury of the thermometer will become stationary. 

 When this is observed, the degree on the thermometer is .read off, as well as the division on the brass scale, s, opposite the top 

 of the mercury. These two values added together give the temperature of the flue, furnace, or other heated space in which the 

 metal cylinder had been placed. With cylinders of copper and iron, temperatures up to 1,800 F. (1,000 C.) can be measured, 

 but with platinum cylinders the limit is 2,700 F. (1,500 C.). 



For ordinary furnace work either copper or wrought-iron cylinders may be used. Iron cylinders possess a higher melting 

 point, and have less tendency to scale than those of copper, but the latter are much less affected by the corrosive action of the 

 furnace gases ; platinum is, of course, not subject to any of Ihese disadvantages. 



The weight to which the different metal cylinders are adjusted is as follows : 



Copper ... ... ... ... ... ... 137 grammes. 



Wrought-iron ... ... ... ... ... ... 112 



Platinum ... ... ... ... .. ... 402.6 



In course of time the copper cylinders lose weight by scaling ; the table which now follows gives for the diminished weights 

 the factor with which the readings on the brass scale have to be multiplied in order to obtain the correct temperature. 



Table of Corrections for the Decrease in Weight of the Copper Cylinders. 



5383 s Siemens' Water Pyrometer, with thermometer 1,000 C. or 1,800 F., and seven copper 

 cylinders, complete 



A5383 5 Siemens' Water Pyrometer, with eight cylinders of wrought-iron instead of copper . . 



B5383 S Siemens' Water Pyrometer, with one cylinder of nickel and thermometer i 400 C 

 or 2,550 F. . . 



Accessories for above. 



A. Spare Thermometer and scale, 1,000 C. or 1,800 F. 

 B - .. ,, 1,400 C. or 2,550 F. 



C. Spare Sliding Scale 



D. Spare Copper Cylinders . . . . . . eac h 



E. Spare Wrought-iron Cylinders .. 



F. Spare Nickel Cylinders . . 



G. Platinum Cylinders (according to market prices of platinum) about 



When ordering spare thermometers and scales please state if required C, or F. scale, and if (or use 



with nickel, iron, copper, or platinum cylinders. 



4 10 

 4 10 



4 10 



CROSS STREET HATTON GARDETST, E-C 



