Throat oj the reservoir: That portion of the 

 capillary from the reservoir to the appendix. 



Tap: To jar from below with the hand or 

 against some object. 



Manipulation: The entire procedure or series 

 of procedures used to remove bubbles from 

 within the mercury column. 



Drain: The flowing back of the mercury 

 from the bulb upon righting the thermometer 

 after reversal, to rejoin the main body of 

 mercury in the reservoir and contiguous 

 capillary section. 



Flood: The type of malfunction described as 

 No. 3 above. 



Correct breaking point: The one and only 

 point at which the mercury column is supposed 

 always to break at reversal. This is the 

 junction of the appendix with the main capil- 

 lary channel, in thermometers having a true 

 appendix (fig. A-la). In thermometers made 

 with a constriction or "collar-button," the cor- 

 rect breaking point will be either at the stem 

 end of the constriction, or at the narrowest 

 part of the channel in the constriction, depend- 

 ing upon the exact shape of the deformed area 

 (figs. A-lb and A-lc). 



A-5 Causes of Malfunctions. — Certain in- 

 struments are more prone to malfunction than 

 others, and the instruments of one manufac- 

 turer may, in general, give more trouble in this 

 respect than those of another. There are 

 found in use occasionally reversing thermom- 

 eters which are basically defective due to the 

 conformation of the appendix or constriction 

 and/or the adjacent capillary, which exhibit the 

 characteristic of breaking at either one of two 

 distinct points in entirely random sequence. 

 These points are generally very close together, 

 so that the temperature difference indicated 

 between a correct and an incorrect break is 

 very small, from a few hundredths of a degree 

 to half a degree. Such an instrument may be 

 considered to be permanently malfunctional. 



The usual cause of intermittent malfunction 

 in a reversing thermometer is the presence of 

 gas (a bubble) within the mercury column 

 somewhere in the capillary system. Normally, 

 whatever gas is present in the thermometer is, 

 and should be, above the mercury column when 

 the instrument is in an upright position. On 

 occasion, however, as the result of transporting 

 or rough handling of the instrument in its re- 

 versed position, such gas, or part of it, moves 

 up through the mercury column, and wherever 

 it settles, will generally cause separation of the 

 mercury at that point when the attitude of the 

 thermometer is again changed. 



162 



When a malfunction occurs as the result of 

 a bubble, and the mercury breaks at some 

 other point than the correct breaking point, 

 manipulation must be undertaken to move the 

 bubble from wherever it happens to be out to 

 the end of the bulb, so that it will be above the 

 mercury when the instrument is in the upright 

 position. This process is well and adequately 

 described in the Richter & Wiese pamphlet 

 "tjber die Funktion der Umkippthermometer 

 sowie die Beseitigung von Storungen," a trans- 

 lation of which will be found in the appendix 

 hereto. There are a few refinements to the 

 Richter & Wiese basic technique, however, 

 which may be of interest, as they tend to 

 facilitate manipulation. 



A-6 Heating Medium. — Instead of a small 

 flame, hot water, preferably running, up to 50° 

 or 60° C. is safer and quicker to use for warming 

 the thermometer when required during man- 

 ipulation. It should, of course, be applied 

 fairly slowly so that the temperature change is 

 not too sudden. 



A-7 Rejoining Mercury Separated in the 

 Bulb. — When a bubble has been moved up 

 into the lower or middle part of the bulb, par- 

 ticularly if the bubble is of any size, the final 

 stage of the manipulation (knocking off of 

 globules of mercury in the bulb) can, in the 

 case of a great many instruments, be more 

 quickly, easily, and safely accomplished in the 

 following manner: 



There being a portion of mercury in the outer 

 end of the bulb, with gas between it and the 

 column of mercury entering the bulb from the 

 stem, hold the thermometer nearly horizontal 

 and allow the two sections of mercury to come 

 very slowly together. When the two sections 

 of mercury meet, joining will begin at the bot- 

 tom side, and the bubble will be squeezed out 

 to the top wall of the bulb (fig. A-ld). Now, if 

 the thermometer is slowly partially righted, the 

 mercury in the bulb will probablj' begin to 

 separate at the point where the bubble was, the 

 separation starting at the top side. As the 

 two sections move apart, the cohesiveness of 

 the mercurj' will cause a certain amount of the 

 outer portion to be drawn along with the inner 

 portion retreating into the stem, while the 

 bubbles move toward the outer end of the bulb 

 (fig. A-le). Relativelj^ few repetitions of this 

 action will move the bubble entirely out to the 

 end of the bulb, where it is desired to be. 



It should be noted that this method will not 

 work with all instruments, and it may be neces- 

 sary to resort to the Richter & Wiese method, 

 but it is worth trying at the beginning. The 

 nearer the trapped gas is to the outer end of 



H. O. 607 



