NATRI BENZOAT  

Natrii benzoas

 

 

 

 

C7H5NaO2 P.t.l: 144,1

Natri benzoat la natri benzencarboxylat, phai cha t 99,0 en 100,5% C7H5NaO2, tnh theo che pham a lam kho.

Tnh chat

Bot ket tinh hay hat hoac manh mau trang, hi hut am. De tan trong nc, hi tan trong ethanol 90% (tt/tt).

nh tnh

A. Phai cho phan ng nh tnh B va C cua ion benzoat (Phu luc 8.1).

B. Phai cho phan ng nh tnh A cua ion natri (Phu luc 8.1).

o trong va mau sac cua dung dch

Dung dch S: Hoa tan 10,0 g che pham trong nc khong co carbon dioxyd (TT) va pha loang thanh 100 ml bang cung dung moi.

Dung dch S phai trong (Phu luc 9.2) va mau khong c am hn mau mau V6 (Phu luc 9.3, phng phap 2).

Gii han acid - kiem

Them 10 ml nc khong co carbon dioxyd (TT) va 0,2 ml dung dch phenolphtalein (TT) vao 10 ml dung dch S. Dung dch phai chuyen mau khi them khong c qua 0,2 ml dung dch natri hydroxyd 0,1 N (CĐ) hoac dung dch acid hydrocloric 0,1 N (CĐ).

Hp chat halogen

Tat ca cac dung cu thuy tinh c dung phai khong co clorid va phai c chuan b bang cach ngam qua em trong dung dch acid nitric 50% (TT), c ra sach va ngam trong nc. Phai co ch dan rang dung cu thuy tinh c dung cho phep th nay.

Dung dch th: Lay 20,0 ml dung dch S, them 5 ml nc, pha loang thanh 50,0 ml bang ethanol 96% (TT).

Xac nh clor a b ion hoa:

Khong c qua 0,02%.

Trong 3 bnh nh mc 25 ml, chuan b cac dung dch sau:

Dung dch (1): Them vao 4,0 ml dung dch th, 3 ml dung dch natri hydroxyd loang (TT) va 3 ml ethanol 96% (TT). Dung dch nay c dung e chuan b dung dch A.

Dung dch (2): Them vao 3 ml dung dch natri hydroxyd loang (TT), 2 ml nc va 5 ml ethanol 96% (TT). Dung dch nay c dung e chuan b dung dch B.

Dung dch (3): Them vao 4,0 ml dung dch clorid mau 8 phan trieu (TT), 6,0 ml nc. Dung dch nay dung e chuan b dung dch C.

Trong bnh nh mc 25 ml th t cho vao 10,0 ml nc. Them vao moi bnh 5 ml dung dch sat (III) amoni sulfat (TT), tron eu va them tng giot, va them va lac, 2 ml acid nitric (TT) va 5 ml dung dch thuy ngan (II) thiocyanat (TT). Lac. Pha loang dung dch trong moi bnh thanh 25,0 ml bang nc va e cac bnh trong chau nc 20 oC trong 15 phut. o o hap thu (Phu luc 4.1) bc song 460 nm trong coc o 2 cm cua dung dch A, lay dung dch B lam mau trang va cua dung dch C dung dung dch trong bnh cha 10 ml nc lam mau trang. o hap thu cua dung dch A khong c ln hn o hap thu cua dung dch C.

Xac nh clor toan phan:

Khong c qua 0,03%.

Dung dch (1): Them 7,5 ml dung dch natri hydroxyd loang (TT) va 0,125 g hp kim nhom nickel (TT) vao 10 ml dung dch th. un nong tren noi cach thuy 10 phut. e nguoi en nhiet o phong, loc vao bnh nh mc co dung tch 25 ml va ra pheu loc 3 lan, moi lan vi 2 ml ethanol 96% (TT) (tua nhe co the hnh thanh roi bien mat khi acid hoa). Pha loang dch loc va nc ra thanh 25,0 ml bang nc. Dung dch nay c dung e chuan b dung dch A.

Dung dch (2): Chuan b nh dung dch (1), nhng thay 10,0 ml dung dch th bang 10,0 ml hon hp ong the tch ethanol 96% (TT) va nc. Dung dch nay dung e chuan b dung dch B.

Dung dch (3): Them 4,0 ml nc vao 6,0 ml dung dch clorid mau 8 phan trieu (TT). Dung dch nay dung e chuan b dung dch C.

Them rieng biet lan lt vao 4 bnh nh mc co dung tch 25 ml: 10 ml dung dch (1), 10 ml dung dch (2), 10 ml dung dch (3) va 10 ml nc.

Them vao moi bnh 5 ml dung dch sat (III) amoni sulfat (TT), tron eu va them tng giot, va them va lac 2 ml acid nitric (TT) va 5 ml dung dch thuy ngan (II) thiocyanat (TT), lac. Pha loang dung dch trong moi bnh thanh 25,0 ml bang nc va e cac bnh trong chau nc 20oC trong 15 phut. o o hap thu (Phu luc 4.1) bc song 460 nm, trong coc o 2 cm cua dung dch A, dung dung dch B lam mau trang va cua dung dch C, dung dung dch cha 10 ml nc lam mau trang. o hap thu cua dung dch A khong c ln hn o hap thu cua dung dch C.

Kim loai nang

Khong c qua 10 phan trieu (Phu luc 9.4.8).

Lay 2,0 g che pham tien hanh th theo phng phap 3. Dung 2 ml dung dch ch mau 10 phan trieu (TT) e chuan b mau oi chieu.

Mat khoi lng do lam kho

Khong c qua 2,0% (Phu luc 9.6).

(1,000 g che pham; 100 - 105 OC).

nh lng

Hoa tan 0,250 g che pham trong 20 ml acid acetic khan (TT), lam nong en 50 OC neu can thiet. e nguoi, dung 0,05 ml dung dch naphtholbenzein (TT) lam ch th. Chuan o bang dung dch acid percloric 0,1 N (C) en khi mau xanh luc xuat hien.

1 ml dung dch acid percloric 0,1 N (C) tng ng vi 14,41 mg C7H5NaO2.

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