Analytical Chem istry - DePauw University

Chapter 1 Introduction to Analytical Chemistry3SolidsSolutionskeyPbSO 4; SandOriginal Sample1:3 H 2SO 4/HNO 3, 100°C for 8-10 hrsdilute w/H 2O, digest for 2-4 hrCu 2+ , Fe 3+ , Co 2+ , Ni 2+Start14 hoursdilute; bubble H 2S(g)Fe 3+ , Co 2+ , Ni 2+CuS16 hourscool, add NH 3digest 50 o -70 o for 30 minFe(OH) 3Co 2+ , Ni 2+HClFe 3+ neutralize w/NH 3add Na 2CO 3, CH 3COOHbasic ferric acetatemass AWasteCo 2+ , Ni 2+Co(OH) 2, Ni(OH) 2heatWasteheat; H 2(g)*slightly acidify w/HClheat, bubble H 2S(g)CoS, NiSadd aqua regia and heatadd HCl until strongly acidicbubble H 2S(g)add Na 2CO 3until alkalineadd NaOHCo, Niadd HNO 3, K 2CO 3, KNO 3,and CH 3COOH and digest for 24 hoursCuS, PbSApproximate Elapsed Time17 hours20 hours22 hours23 hours26 hoursNi 2+ K 3Co(NO 3) 5add dilute HCl51 hoursmass BCo 2+Cofollow procedurefrom point * aboveWaste%Ni =mass A - mass Bmass sample x 100Figure 1.1 Fresenius’ analytical scheme for the gravimetric analysis of Ni in ores. Note thatthe mass of nickel is not determined directly. Instead, Co and Ni are isolated and weighed(mass A), and then Co is isolated and weighed (mass B). The timeline shows that afterdigesting a sample, it takes approximately 44 hours to complete an analysis. This schemeis an example of a gravimetric analysis in which mass is the important measurement. SeeChapter 8 for more information about gravimetric procedures.54 hours58 hours