第24部分(第6/7 頁)

h　only　12　students　in　the　Chemistry　group；　the　school　took　us　as　elites　and　a　certain　teacher　was　appointed　to　direct　us　into　the　world　of　Chemistry　（Our　class　is　different　from　others　class　because　it　is　formed　by　three　groups　and　each　member　was　selected　from　a　special　entrance　exam　given　by　the　school）。　Also　because　our　main　task　is　to　pete　for　the　first　prize　in　national　or　even　international　petitions；　every　property　of　a　new　element　or　material　we　learn　about　always　es　by　means　of　a　series　of　exploratory　experiments　through　which　we　were　able　to　learn　knowledge　by　heart。

In　the　past　few　days　we　h*e　performed　a　series　of　experiments　in　an　attempt　to　know　the　properties　of　the　elements　of　the　halogen　family；　in　which　the　members　are　all　oxidizing　agents。　Belonging　to　the　halogen　family；　fluorine　is　the　most　active　nonmetal　in　the　periodic　chart。

When　I　mixed　the　solution　of　Cl2　and　Na2S　together；　a　lot　of　black…yellow　deposit　was　formed　in　the　solution　and　then　precipitated　to　the　bottom　of　the　test　tube；　which　was　considered　as　S　according　to　the　introduction　of　Chlorine　in　the　text　book。　As　we　added　more　solution　of　Cl2；　those　deposits　vanished。　Deeply　attracted　by　the　unexpected　and　illuminating　phenomenon；　I　wondered　how　to　explain　such　an　observation。　Two　plausible　hypotheses　were　formed　in　my　mind：　Cl2　is　a　strong　and　ordinary　oxidizing　agent；　the　product　S；　which　is　the　black…yellow　precipitate；　may　h*e　been　oxidized　by　sufficient　Cl2　to　bee　SO2…3　（hypothesis　1）　or　SO2…4　（hypothesis　2）；　which　are　all　soluble　ions。　Hypothesis　1　may　be　possible　had　it　not　for　one　factor：　BaCl2　solution　is　poured　into　the　mixture　and　white　precipitate　not　soluble　in　nitric　acid　is　formed。　Thus　that　proves　that　hypothesis　2　is　true。　Then　a　problem　is　resolved；　I　man