OX OXYAMIDOSULPHOXATES. <227 



them into sulphite and hyponitrite, neither of which give« a cuprous 

 precipitate in presence of alkalis. 



We have vet to supply particulars of our quantitative work. 

 The amount of sulphite produced was imperfectly estimated unavoid- 

 ably, partly because of the great oxidisability of the very dilute 

 alkaline sulphite by air, and partly because of the always incomplete 

 decomposition of the oxyamidosulphonate. To measure it, the 

 mother-liquor of the copper precipitate was run into excess ofhalf- 

 decinormal iodine-solution (mixed with acid enough to more than 

 neutralise the alkali in the mother-liquor), and the unconsumed iodine 

 titrated with sodium thiosulphate. All the water used was previously 

 freed from air by boiling. Of the salt, 1.0967 grams, treated with 

 copper sulphate and potassium hydroxide, gave in this way 40 % 

 of the sulphur of the salt as sulphite, and that was our best result. 

 Theory, as given by us, indicates 50 %, while on the other view 

 there should be none at all. Other portions of the mother-liquor 

 of the copper precipitate were acidified for hydrolysis of any re- 

 maining sulphonate, and concentrated by evaporation. One of these 

 then gave quite a distinct further reduction with the copper mixture, 

 due to hydroxyamine, while another measured portion showed on 

 titration with iodine in presence of potassium-acid-carbonate the pre- 

 sence of hydroxyamine, equivalent however to only one-twelfth of the 

 whole salt. 



To measure the amount of copper reduced we added to 0.2913 

 gram of the salt (already very slightly hydrolysed, by keeping), dis- 

 solved in water, a sort of Fehling's solution, much stronger than 

 usual and with much less alkali in it, in slight excess, heated to 

 boiling to collect the cuprous oxide, filtered, rapidly washed, and 

 weighed the reduced oxide as black oxide. We thus obtained cupric 

 oxide equal to 48 % of the weight of the salt instead of 47 % , 



