. American engineer and railroad journal . erature of 120°to 130° F. If no precipitate separates at the end of this time,the filtrate may be thrown away. If any precipitate shows,allow to stand over night, collect on a filter, wash thoroughly,ignite and weigh, adding the weight to the amount previouslyfound. Allowing the precipitated sulphide to stand in a warm placeover night may be unnecessarily long, but as all the constitu-nts of a phosphor-bronze are usually determined, allowiug thetin to stand over night does not usually cause any delay. Itseems to be essential to have the H2S pass off b
. American engineer and railroad journal . erature of 120°to 130° F. If no precipitate separates at the end of this time,the filtrate may be thrown away. If any precipitate shows,allow to stand over night, collect on a filter, wash thoroughly,ignite and weigh, adding the weight to the amount previouslyfound. Allowing the precipitated sulphide to stand in a warm placeover night may be unnecessarily long, but as all the constitu-nts of a phosphor-bronze are usually determined, allowiug thetin to stand over night does not usually cause any delay. Itseems to be essential to have the H2S pass off before filtration,since the precipitate is sparingly soluble in solution of sulphu-retted hydrogen. In washing the tin sulphide, it is essential to remove the am-monium chloride completely, or loss of tin will follow duringthe ignition. By the method of washing recommended, lessthan 5 per cent, of the total amount of ammonium chloridepresent remains with the precipitate Vhen it is put on^thefilter. SECTION A B. fPONT VIEW C0UPUNG5 UNITEO. COUPUNC HEAO Fig. I. It is very difficult to wash tin sulphide mixed with separat-ed sulphur with pure water, on account of the tendency toform a turbid filtrate. As is well known, a slightly acid solu-tion of acetate of ammonia prevents this difficulty. It is ad-visable, at the very last, to use a much weaker solution of am-monium acetate, so as not to leave too much of this salt withthe tin sulphide for fear of reducing some of the tin oxide dur-ing the ignition. The ignition of the wet tin sulphide must be managed witha good deal of caution or there will be either loss of tin sul-phide, free sulphur, or sulphuric acid left behind, or some ofthe oxide of tin reduced. It is believed all these difficultiescan be obviated if the ignition is done slowly enough withfree access of air. The filter is gotten rid of by smokingoff, which consists in applying the heat to the wet materialin the crucible so slowly that the volatile matter of the filterp
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