CHEMISTRY: BAXTER AND STARKWEATHER 
719 
being an ingot of tin. This served at the same time to eliminate a 
large part of the copper and lead which were the chief metallic impurities . 
The product was fused in hydrogen on an alundum boat. 
In preparing the tetrachloride special pains was taken to avoid ex- 
posing the substance to moisture. The ingots of metal were placed 
in a glass tube connected at one end with an apparatus for producing 
dry chlorine and at the other with a glass bulb containing a small quan- 
tity of tin. After the tube and bulb had been exhausted dry, chlorine 
was admitted and passed over the metal until it had been almost com- 
pletely converted to chloride. The product was allowed to stand in 
contact with tin for some time to remove excess of chlorine and reduce 
lead tetrachloride, and was then fractionally distilled in vacuum at 
room temperature by condensing the product in bulbs cooled either with 
alcohol and solid carbon dioxide or with liquid air. First the most 
volatile fraction was removed with liquid air and rejected. The re- 
mainder was four times distilled, with rejection of a residue of about 15 
grams in each case. Then two more fractions were eliminated with 
Kquid air. The remainder was finally collected for analysis in a series 
of small bulbs. In the course of the distillation each fraction was 
sealed off from the rest of the apparatus as soon as collected. Two 
series of preparations were made, the procedure differing only slightly 
in the two cases. 
The whole apparatus was constructed of glass, with sealed joints, 
the only glass stopcock was located between the tube containing the 
tin and the chlorine generator, and was lubricated with syrupy phosphoric 
acid. In place of stopcocks special glass valves devised by Briscoe 
were employed, in which a fused seal was broken when it was desired 
to open the valve. 
The experimental procedure of an analysis was as follows: The glass 
bulb containing the stannic chloride was weighed in air, and again 
under water to find its displacement. Next the bulb was broken under 
about 75 cc. of 0.03 normal hydrochloric acid. The solution was then 
filtered into the weighed cell containing about 200 grams of mercury, 
and the glass was thoroughly washed with hydrochloric acid of the 
above concentration. The filter with the glass was burned in a weighed 
platinum crucible. Blank tests showed no appreciable quantity of 
glass to be dissolved in the process. The more concentrated washings 
were added to the main solution in the cell, the more dilute were evapo- 
rated with nitric and sulphuric acids in quartz. After nearly all the 
tin had been electrolytically deposited from the main solution, the resid- 
ual electrolyte was concentrated, together with the evaporated wash- 
