1889.] On certain Ternary Alloys. 465 



jacketted temperatures varying in different experiments between 

 550 and 580, and averaging exactly 565 ; whilst when heated in 

 pipe bowls jacketted with the cylinder, temperatures were indicated 

 varying between 675 and 705, and averaging 689, or 124 higher than 

 before.* It may therefore be fairly assumed that the average tem- 

 perature at which the mixtures were kept molten was not far from 

 124 higher in the second series than in the first. 



After the requisite time had elapsed the lamp was removed, as also 

 the jacketted cylinder when employed ; in a few minutes the contents 

 of the pipe-bowl were solid, when the clay was broken away from the 

 somewhat conical compound ingot formed. After filing away about a 

 couple of millimetres from the outside, the top and bottom portions 

 were cut off by a cold chisel or saw and analysed. Usually a well- 

 marked line of separation between the heavier and lighter alloys 

 formed and was easily distinguishable ; as long as the tin percentage in 

 the total mass was low, this line was approximately in the middle of 

 the mass, but with larger proportions of tin the dividing line gradually 

 rose until the limit was being approached, beyond which no separation 

 took place, when the dividing line was so near to the upper surface as 

 to render it impossible to saw off even a thin layer of lighter alloy 

 without intermixture with more or less of the heavier one. 



The analysis in all cases was made as follows : a weighed portion 

 (usually from 5 to 8 grams) was boiled with diluted pure nitric acid 

 in a well-covered capacious beaker until complete oxidation was 

 effected ; the liquid was then diluted and allowed to stand till cold 

 and filtered. No appreciable quantity of tin was ever found in 

 solution. t The filtrate was evaporated to a small bulk with excess of 

 pure sulphuric acid, and the lead sulphate produced collected and 

 weighed; the filtrate and washings from this sometimes contained 

 traces of lead ; if so, these were precipitated by sulphuretted hydrogen 



* The calorimeter employed contained a litre of water and had a water equivalent 

 of 1050 grams ; the thermometer read to -^ of a degree centigrade. Taking the 

 initial temperature of this calorimeter as 1} and the final as 2 (corrected for radia- 

 tion, &c.), W as the weight of platinum, and S its mean specific heat between t 2 and 

 T, the temperature to be measured, the value of T was calculated by the formula 



IQSOxfe-fr) 



~w7s~ 



W in most of the observations was 51*055 grams; S was taken from Pouillet's 

 values by interpolation as being 



Between * 2 (about 15) and 565 = "03545 



689 = -03595 



750 = -03625 



f When tin is oxidised by dilute nitric acid in presence of relatively large quan- 

 tities of certain metals, especially iron (e.g., in the case of tinplate), very perceptible 

 quantities of tin are generally taken permanently into solution. 



