Translation Series No, 3151

FISHERIES AND MARINE SERVICE

The properties of cadmium-type pigments and pollution control during their manufacture \

by Makoto Tsunashima

Original title: Kadomyumukei ganryo no tokusei to seizo ni okeru kankyo taisaku

From: Kagaku Kogyo (Chemical Industry), 24(12) : 1579-1585, 1973

Translated by . the Translation Bureau( JM/pS) Multilingual Services Division Department of the Secretary of State of Canada

Department of the Environment Fisheries and Marine Service Biological Station St. Andrews, N.B. • • 1974

21 pages typescript -1

SECRÉTARIAT D'ÉTAT DEPARTMENT OF THE SECRETARY OF STATE BUREAU DES TRADUCTIONS } TRANSLATION BUREAU It MULTILINGUAL SERVICES DIVISION DES SERVICES CANADA DIVISION MULTILINGUES r1s, -4-, 5 0 6- (

TRANSLATED FROM - TRADUCTION DE Js.,) an ese I English AUTHOR - AUTEUR

T-_a'_wto Tsunashima TITLE IN ENGLISH - TITRE ANGLAIS The Properties of Cac1n)ium-type Pigments an-? Pollution Control during Their Yanufacture

TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE ETRANGÉRE (TRANSCRIRE EN CARACTÉRES ROMAINS)

Kadomyui^:ukei ^,anryo no tokusei to seizo ni oker•u kankqo taisaku

REFERENCE IN FOREIGN LANGUAGE ( NAME OF BOOK OR PUBLICATION) IN FULL. TRANSLITERATE FOREIGNCHARACTERS. REFERENCE EN LANGUE ETRANGERE (NOM DU LIVRE OU PUBLICATION). AU COMPLET, TRANSCRIRE EN CARACTèRES ROMAINS. i:a;aku Iiog,-yo, Vol. 21^, NTo. 12, 1,?73•

REFE.RFNCE IN ENGLISH - REF'cRENCE EN ANGLAIS

C:1CT[i? cal Z11d.l.tstrÿ

PAGE NUMBERS IN ORIGINAL PUBLISHER- EDITEUR DATE OF PUBLICATION NUMÉROS DES PAGES DANS DATE DE PUBLICATION L'ORIGINAL pp. 1579-1585 YEAR ISSUE N0. VOLUME ANNEE NUMERO NUMBER OF TYPED PAGES PLACE OF PUBLICATION NOMBRE DE PAGES LIEU DE PUBLICATION DACTYLOGRAPHIEES 1973 12 21

TRANSLATION BUREAU NO. REQUESTING DEPARTMENT 784420 Environment NOTRE DOSSIER NO MINISTÉRE-CLIENT

TRANSLATOR (INITIALS) BRANCH OR DIVISION JM / PS Fisheries Service TRADUCTEUR (INITIALES) DIRECTION OU DIVISION

PERSON REQUESTING Allan T. Reid DEMANDE PAR AUG 19 1974

YOUR NUMBER UNEDITED TRANSLATION VOTRE DOSSIER NO For information only

DATE OF REQUEST 05-06-74 'TRADUCTION NON REVISE-E DATE DE LA DEMANDE lnforma1ion seulement

SOS.200-1 0-0 (REV. 2/68) 7030-21-029-8333 £1.9 ' fiEPARTMENT OF THE SECRETARY OF STATE SECRÉTARIAT D'ÉTAT

6 TRANSLATION BUREAU BUREAU DES TRADUCTIONS

MULTILINGUAL SERVICES DIVISION DES SERVICES DIVISION MULTILINGUES

CLIENT'S NO. DEPARTMENT DIVISION/BRANCH CITY N° DU CLIENT MINISTÉRE DIVISION/DIRECTION VILLE, , , . Environment Fisheries Service Ottawa, Ont. BUREAU NO. LANGUAGE TRANSLATOR (INITIALS) LANGUE TRADUCTEUR (INITIALES) N° DU BUREAU AUG 1 9 1974 784420 Japanese JM / PS

Kadomumuei ganryo no tokusel to seizo ni okeru kankyo p. 1579 taisaku (The properties of cadmium-type pigments and pollution control durini-ri; their manufacture). Makoto Tsunashima* Kagaku kogyo (Chemical industry), Vol. 24, No. 12, 1973.

1. Introduction The cadmium-type pigments are a series of pigments which contain as their major components cadmium sulfide (Cd3), zinc sulfide (Zn3), cadmium selenide, mercury sulf-

ide and barium sulfate. They possess a continuous and vivid spectrum of colours from yellow to red to maroon end they

have excellent heat-resisting and weather-resisting prop- z uJ o erties. —a The history of cadmium sulfide as a yellow pigment zolee o -91z '42 z is long. It is a matter of record t'aat grecnockite (Cas) z g .42 and Bohemian mineral deposits was used Lu obtained from Greek - • b. a Ô ° es a yellow colouring material. w U. about two thousand years ago Z oci

f-- * Makoto Tsunashima: Kead, Technical section, Omiya factory, Mitsubishi Kinzoku (metal) Co., Ltd.

SOS-200-10-31

7530-21-029-5332 In 1817 Strohmeyer separated cadmium metal for the first time. The follow!_ng year Gay-Lussac l) .obtained for ç the first time the precipitation of cadmium sulfide from the reaction of hydrogen sulfide in a solution of cadmium chloride.

Early in the twentieth century it became possible to manufacture pigments stable at high temperature through heat treatment of cadmium sulfide obtained by the precipitation reaction. .',11ch pigments are still used today. dowever, cadmium-type pigments became really noticeable from about 1953 .,;hen their excellent prooerties of heat resistance, weather resistance and dispersion as a colouring material became recognized in connection with the th.creased use of plastics. The demand for cadmium-type pigments increased as the plastics industry expanded. Furthermore the cadmium-type pigments have been established as the best yellow and red pigments for use under severe conditions (especially with regard to temperature) during the manufacture of plastics. 2. Classification The cadmium-type pigments are classified roughly as the yellow types and the red types. The yellow types are CdS and the solid solution of CdS and ZnS. Colours change continuously from yellow CdS to light yellow with the increase in the amount of ZnS in the solid solution. 3

The red types are divided into two kinds: the solid solution of - CdS and CdSe and the solid solution of CdS and HgS. Both have colours which change continuously from yellow CdS to orange to red to maroon with an increase in the amount of either CdSe or UgS in the solid solutions. Cd3-ZnS and CdS-CdSe types are heat resistant up to 500 ° C. The CdS- • UgS types are heat resistant only up to 350° C because of the low heat stability of HgS. Generally the products which contain only the colouring components stated above are called chemically pure types. The products which contain about (..3 /0 of barium sulfate as a filler in addition to the colouring components stated above are called Cadmopone types. The cadmopone types are used mainly in the U.S.A. and the chemically pure types are used mainly in Japan. The compositions and their colours are given in Table 1. Product compositions and names differ only slightly according to makers. In the most recent reports,CdS and CdS-ZnSe 2) of

I type and CdS-Cd3e 3) have been mentioned, however, these products had so far almost not appeared on the market. These p. 1580 pigments are of crystal form and stable at low temperature. The colours change when the temperature exceeds 500° C;on the other hand dispersion . is good. These pigments can with- stand the processing heat of plastics so that their future development should be expected. The yellow-oranges which 4

Table 1 Compositions_ Of c ^.:3miu:n- Pe lt ; Yellow types Red tvnes (AIS 1 i lg5 , BatiO, iVTa Ii1e.`.;'^ " Cdti "LnS llilS09 iì es Cds 1 Cdse I3n5oa?Tt me S t12 1 t3 ^ Pale 74 26 - Ur•an,,;e ► - c)rarlge !m lu 11) i tT'n t 81 17 r,1^rt 8fS 1 - L1-P5flt G9 31 `_ x, T,'id^?le 100 - - 1iidd.le 58 42 - T"S_r3d, e W 20 50 Oran ,e':2 (cdcO, 5sj aroon 50 'T^roon Cadmiorx^:1e ^ 9 C^^.ClÔ êône CHdnrolD -) nE 36 4 1 60 Lemon 31 GU 0r^.ng e Orange ^ a'L i B GO Li^;'.^t 3`, ^^ Go Lis^;at I 01) T.,1.j;[lt 16 j GU ;1^^j18 3u GO Yellow 40 - Go middle

:1 Nar,.es differ according to ma?kers .:2 Yellow-orange is a mixed composition of CdS-CdCO3 have CdS-CdCO3 components (Table 1) are seldom used as they havé lesser Iieat- and weather-resistances due to the presense of CdCO3.

CdS, ZnS, CdSe and H,r^S, the colouri n'. ingredients of cadmiurri-type pi;,ments, have very similar crystal structures and form solid solutions throuiout. These crystals

are of two t rnes: â type (W,.),rtzite) tia?^ich is stable at hi^n

temperature and ^6 type (Zincblende) which is stable at low

terap erature. 3otn c.r.ystp.ls coexist strbl^ wit.nin the range o from s. normal temperature to 500 C. In a recent report -lat F, rock salt type structure also it was confirmed t ► exist at high pressure1^ w 7).

The correlation between the crystal structures or

the solid solution inc-retai ents and colour have been dis-

cussed in the past. Khan et a.1.8) and Davis et al. 9)

have reported on the yellow CdS-ZnS type pigments. They Table 2 Lattice constant and exclusion band width for endmiu,-tyee oiments Crystal d type e type - Colours Colours Irlo'red- P- a, 1 cu 1 I.:, tLenow au )range - / White - /White cds 4.11 ' 6.72 ' 2 53 7 ., 5.82 2.50 , ZnS • C 3.82 6.211 3. 87 f 5.11 1 3.713 ,,,eedish- CdSe. 4.30 7.01 1.85 /0- dra sh - 6,511 1. 1.81 brOW21. 1 lei .1.15 1 9.50 '2.19 5.85 2.10 /br°n explain that during the formation of a solid solution, the lattice constant and the exclusion band width change continuously according to its ingredients. The change is correlated with à continuous chanF,e, of colaurs. Friedberg et al. 10 ) and 11) Cndo et al. reported similar findings on the red Cd- %S type. The CdS-ligS type pigments are pigments newly developed in America since 1955 in order to make up for the shortage of Se. Detailed reports have not appeared, however these pigments are presented occasionally as patents 12 ce' 13) Continuous chanc'Esin the solid solution of crystals and in their colours are observed in the cases of CdS-ZaS and CdS- CdSe typo pigments. There are some reports on red CdS- CdTe type solid solution pigments 1 4). The CdS-CdCO2 type orange pigments are not solid solutions but a mixture of CdS and CdCO3; colours are also mixed. The cadmium-type pigments presently on the market are mostly o( type with crystals stable at high temperature. Recently CdS, CdS-ZnS types 2) and CdS-CdSe types 3) have been reported to be pigments with ,e type crystal structure. 6

A: yellow 3: red pale orange light light middle middle s. • maroon c H f CI 4 I CV rf

wau e n g -th ( nli4 " ) Fig. 1 Curves for spectral reflection rate for the cadmium-type pigTeents

The 5type crystal structure is stable nt low temperature. Therefore when heat treeted, it changes multiformally to at type thus brin;ing a change in colour. This change occurs at over 500 ° C; therefore these pigilents are suffi- ciently heat resistant for ordinary usage with plastics. Otherwise characteristics are similar to those of the ce type pigments. The dispersion to plastics is said to be better than that of cp< type. The chemical propexInes of colour ingredients are given in Table 2. The curves for the rate of spectral reflection of the yellow-red-maroon pigments (Table 1) are given in Fig. 1. 3. Manufacture Two methods are used for manufacturing the cadmium- type pigments: the wet and the dry methods. At present the wet method is used most as it produces stable and efficient pigments. p. 1581 cadmium sIt zincic salt alkali sulfide, or mercuric or barium 1 salt sulfide mixed solution

I . wash, filtration dry calcination - 7wash_ , filtration_ dry • pulverization pigments Fig. 2 Manufacturing process.for CdS-ZnS type and CdS-HgS type pigments

Wet method cadmium salt selenium alkali sulfide or barium sulfide 1 I resolution _

reaction (The following is the same as those given in Fig. 2.)

Dry method • cadmium carbonate sulfur selenium • mixture • L calcination (The following is the sarde as those given in Fig. 2.) Fig. 3 Manufacturing process by wet and dry methods of CdS-CdSe type pigments 8

Manufacture by the wet method is divided roughly into two processes: the precipitation reaction process and the calcination process. The difference between the wet and the dry methods lies in the composition of powd.ered mixture produced by the precipitation reaction and that of the mixture produced by the dry method. The ma.iufactur•ing process for the yellow cadmium pigments is given in Fig. 2.

The colours of pigmerits are mostly determined by the pro- portion of Cd and Zn durinD, the precipitation reaction.

'?owever, the heating temperature, time and atmosphere during

the calcination pro-le ss also affect the size and shape of

particles and the distribution of particl erHameters. These

also lori,ig ciZani;es in colc)üi's (tone, ûrig!..,t-ss and chror.A).

In r^igr. CdS-HgS type r•ed pigments are obtained when mer-

curie salt solution is used instead of z;.Tîcic salt solution.

The major difference in the manufacturing of CdS-ZnS type

and CdS-_H^^S lies in the calcination process. The calcination

temperature for the CdS-ZnS type pigments ,(yellow) is 5O0-

ECJ°C and is below 37^ C for. the CdS-%^S typo pigments (red)

since the heat stûbility of HgS is low.

The manufacturing method for the Cd2-CdSe type pig-

:ne^its 1s the sarr.e as the above. In i^art;_cula.r, the process

following the precipitation reaction is the sawe as given

in Tig. 2. Ther°fore the process up to the reaction is

given i n T1F• 3. C,^S-rdSe type r Cd pi gs'i:e ;llu-s are ^^à.ve;.1 as

an example for the dry fr:etho,^. In this case the calcination

0 temperature is 63J-730 C and the reaction of CdCO3 and Se ',- occurs during this process. Generally, in the wet method, cadmIum sait, zincic

salt and mercuric sait are used as sulfates, nitrates and hydrochlorides in the primary solution. Sodium sulfide and barium sulfide are used as tbesulfur compounds. Ammonium

sulfide can be usedbut its composition is unstable. In the case of hydrogen 'sulfide gas, it is costly in that it requires expensive gas absorption equipment. Variations in the solution during the reaction affect the precipitation process as does the addition or special salts. The charac-

. teristics of the manufactured pigments are also affected in these ways. Many patents are elaracterized on this basis 15) . Selenium is usually used in the form of alkali sulfide solution. The precipitate formed is calcinated after it is washed and dried. The air surrounding calcination is a sulfide getting

,easily oxidized, therefore, the precipitate . should be of .a non-oxidizing nature. p.1582 Another important process is pulverization. The crystal particles tend to produee .lattice distorsions when . ee ground. As a result the colour becomes dark and cloud 16& 17);- This phenomenon is observed especially for particles Which cohere strongly. Recently a counter- measure has been taken against discolouration during the calcination process. During the pulverization process the 10 discoloration can be lessened if shock rather than grinding is used for pulverization. L. Countermeasures against environmental pollution caused by cadmium During the manufacturing process of cadmium-type pigments, three types of waste are produced. They are (1) powdery dust, (2) water waste and (3) solids (powdery). These can cause environmental pollution. It is essential in order to continue the manufacture of pigments to keep the above three wastes under control at all times and also treat them according to a disposal standard. The following are the typical countermeasures presently practiced for the three wastes above.

4.1 Countermeasures for powdery dust Generally countermeasures for powdery dust(causing. silicosis, for example have been . studied widely for a long time regardless of the question of the degree of toxicity

of the dust components. Therefore disposal equipment has been already in use. It is possible to meet the projected control conditions by combining improvements of existing equipment. In the case of cadmium-type pigments, the powdery dust disposai process given in Fig. 4 is used in order to meet the Conditions determining that the operational environment standard should be below 0.1 mg/m 3 and that the discharge 11 poWdery oust hood - - 1 fan - mnste water bi, filter - - - - 1----wash - - > dIsposal Nif 1 absolute filter - - 1 -' exhaust1

714';-.. 4 Powdery dust disposal process waste water thickener coLo!--;lon tank press filter 4/ 'smelter inspection of waste water , uretreatent) disùharge

Fig. 5 Uaste wat ,Dr dlschcre process standard should be below 1 mg/m3 . According to this method, the powdery dust produced in vaIious places in a factory is sucked in by the local exhaust equipments, the dust is eollected by bn zi-, rilbe -Ps, then is passPd tilrouf:,h the absclute filter pnd f:T.nally is exhausted. The cadmium compound collected in each equipment and duct is wP,sned Pad is either sent to the waste water disposal process or is disposed of as wastes as explained

2,, 1 ') U.11. I ,J• 12

^ -- n17s;.. • .L' i:'tC Pr Ca_i E,q ii _',r'in lt

I.^ t'i: :aste T^^ter dis; osal prccc^s: ; t,,(-. ^^-^.rticle = sha^+ed

an(' T.,, ;t^1' ^ l'_îb 1 t? C^ C':)i'_l_'1 C:'1 ? O ^l: î' ; t'.'1 ^:: a ^;. n^ 's7 a t o I' and in the cooling water are precipitated and then removed. As

s[ioitir.. in IP1 gi. the solid cr'7ri1.u-f1 CSO7y1?Jou_7 -Ts are precipi.tated

and. removed as muc^z as possible, using a thict. ener. Alumi-

ni.}:-m sulf;_t;y,. a C7iherive agent and c^: CaCl-,riui7i precipitant

are added co the sup(,,r•-natant solution côntaining thé côrpus=

cular cadn,:i,_ni c,)crpounds and water soluLle cadmium coiri-

pou_ids. Then the cadmium C>reci-Aate is filtered as a condensed

mass.

^'^>e waste ,,ra},er Is =i.nspected a t a!",- times usi.i•7 an

concentration c^.^^:111C absorption ` nalyfiis, 14hP,n Itno

ris-es . )V^r ij,1 -,l.m which is the discharge standard và3ue; then

t!-^ ;.a;;^.ste water goes throug:, a t-iicriecler a_zl is treated again.

The filtrate ( calte) contaitiing cadmium is sent to

a smelter as raw ore.

4.3 'daçte ^-3i.r-posa1.

The cadmium we.stes Sahicir, elre pror3ucecl by the dis-

posal ekj,.iip:re.its and by the treatment OP the foregQing pow= c^tcd dery dustAwaste water are divided into wastc which ban be

reclaimed as raw ms_tilrial for pigments by ^ ûci _l dis-

so.lut i o.z and waste which is more profitably treated

as a smelte.ri.ng nlater•5.al.

P.r. ese_ztly th e 1:}1ree proCF:3fiC?fi stst^t(l above are us efi

1S met^ °L1CCG'SS^^111^ 2_lCa. the e!lvi7^.-)?1rTlt^ïllr:l t2_l1:3^:11. 13

Therefore the pign_ents are produced under stable conditions. Characterlstics and uses C71racteristIcs of cadmillm- type oients The general pigmentai characteristics of cadmium- type pigments are given in Table 3. The following are especially outstanding characteristics. (1)_ileat resistance: 500 ° C, however, when HqS is contained 350 ° C. (2) Weather resistance: especially good in red p. 1583 type containing CdSe.

(3) Alkali resistance: hardly changes. (4) Solvent resistance: stable against most solvents.

(5) Electrical inrulation: when pigments are mixed with resin for coverinis electric wires, their peculiar volume resistivity value is about 10 1411-cm and is 10-100 times greater than the other pigments.

(6) Dispersibility for plastics: dispersible for many plastics.

(7) .;illality improvement for plastics: when mixed with certain plastics, the pigments can prevent de- terioration of quality and can improve the plastic quality. Special attention should be paid to the following. (1) A portion of pigments gets extracted when soaked in an acid solution of pH value below 3. (Cf. Table 4 when mixed with plastics)

Table 3 Characteristics of cadmium-type pigments *

Discription 1 ••• 10 Item 1 - 10 - 9; v Il I. '4 9;F: ! JI V .7 f ,b, ▪J. vh:e 9 F :V- Lit/ ▪ 9 1 h r

f. q: in Mi. xCcIS. I xecIS. CIS xCilS. xedS. xecIS. xCdS. NC(IS. x( .(1S. .(IS. ; yZnS yZnS y(:(1St. yCtISe C(ISt: y .yZnS I ILaS ( ) )('‘Itit• zliaSO, - ./BaSO4 4-45 4,52 4.58 4.38 4.8 4.9 5.0 5.2 4.50 4.58 i 5, cc/100g 310 300 300 360 290 260 240 230 250 250 ' 255 re. (-- i3:11 sf) P 0. 1 0. I 0. I 0. 1 0. 2 O. 3 0. 4 0, 4 0, I 0. 1 0. '3 e 30 '30 30 60 33 33 33 33 '35 26 27 4 4 -).; mig 110 150 160 100 700 1,000 1,080 I, 100 50 80 400

iil (15.: 100Iws A A A A. I ■!, AI A A ; A A 500 500 500 200 500 500 500 500 500 500 500 i 112SO4 2% A A A A A A A A • , A A A A A A A A A -Ale\ 1J A HNO, 29,; A A A A A A A A ; A 1 A 5F(') A A A A A A ,AjA HC1 2% A A A A A A A ,1 A i A 5°0 A A A Ale\ I A!A ! 2% A A A A A A A .A , A 1I .A • 5.% A A A A A A i AIA IA

7' it A A A B I A A Ai A rAl (1;/11;) 5% Na 01.1 I •

Discription 1. Ca mium yellow pale 2. CadMiumCadmium yellow net 3. Cadmium yellow middle 4. Cadmium yellow orange P. Cadmium red orange 6. Cadmium rod ligt 7. Cadmium red middle 8. CadpliumCadr, ium red maroon 9. CadmoCadme oneono yellow 10. Cadmopone red Item 1. Chemicql composition 2. Specific gravity 3. Volume cc/100 g 4. Mean particle diemeter (the primery particles)Ma 5. Oil absorption cc/100 g b. 'Ming power cm/g 7. Weatner resistance, weathermeter 100 hrs 8. He.?t resistance ° C 9. Acidity resistence (powder) 13. resist?nce (powder) 4 15

„ (i F3^i1Ji7^ of trlv'as+Llre'_1.entS) Specif i c „r°evit;r r°.e-R::ured by JIS-1{5101 Volume -cneastzred by j I3-.K5101 Oil absorption measured by JIS-K5101 il^;ltl û(?O1:1Hr 1;_nas.LrCyd 1>:^ J I`_i-i:51J1 T^iecc.''l. p;.rticl.e d1 :'.rrrtE;r measured fro_rr photographs usi'_Zz; ,an ellectron -microscope

(Notations for weather resistance) A; No ctlailco (utlt^er 0. ."5 w^b^) 3: Slight discoloration (0.5-3 NBti^) C: Discoloration above 3^^TBS

(P•"easurin; condition for acidity resistance and. alkali res, is t=zil ce) t,• 7rg of powderyT oi„rre.ztâfr tr;^.r^,^^ soa^' ,ed for 1J n._nutes at room tarrp'er•a.ture in :r;)0 cc of solution of each concentration given in the. ttlab7.e. Tien each ssmiple was washed, dried and soreGd then compared by unaided eye arid by using a colorimeter.

(2) Sonretirrrés! tl,e ct5lour• bleckens due to the for:^^-

in^; of r'o ^ when used *^Tit^l r. !a -,,,,e nttrount of lcad-t^rpe

P i `;?12c3I1 t s .

(3) Discoloration occurs .vT'zen processed at over

3-5^ C in case of pigments containin;; `igS and at over 500^C

in case of other pigments.

(4) ':+'nen colour^.n^:, a hard vinyl chloride ra sir; ti^

pigments containing ZnS in high concentration at temperatur•e

over decomposition of the resin is accelerated and

sometir:es black-green spots are formed.

(^) '-%Ilzen titanium oxide and the pigments contain-

ii1`; ZnS are used to^;et:^er, the ?•rea.tklFr resistance deteri-

orates and the colour fades due to titaniuz,r action.

(6) The pi 0gments a re easily oXiC^1.Ze(j by o:fi]_C^i?Irlg

a`;ents. 16

(7) Wte.n handling large amounts similar to those of other heavy metals, attention should be ç p s i d since they contain cadmium, selenium and mercury. It is necessary to wear pfloves end dust masks when handling powdery ,?i t>cnts. Table L. Chemical resista£ice test of coloured resins by p. 1584 cadmium pigents'''' (Unit: mg/e--) cds zns CdS Cd CdS IlgS - •

-LI ?es e ez I Solvent R e si n Cd Zn Cd Se Cd 11g PVC 1-5

r 1,letal extraction from coloured resinS When cadmium-type pigments Pre mixed with plastics, metal is extracted from the resin fragments. The amounts of extracted metals are seen in Table 4. The amount is great in the case of pi;.pients containini- 7IgS but very small in other pigments. Selenium is a poison except when useff! medicinally. A simple substance, its oxides and gaseous compounds are 17 harmful. CdSe compounds are usully extremely stable. They do not get extracted when mixed with plastics. In piments, mercury occurs in the form of Pure le is excluded from the specific chemical substances classified as poisons. However, it should not be soal; . ed in a very strong acid or used at high temperature. Generally, the cadmium-type pigments with compo- nent CdS, ZnS, Cd3e and He are in solid solution. Usual- ly they are stable even in the case of He which is most unstable against acid and heat. Therefore if contact with a strong acid is avoided, the cadmium-type pigments can be used chemicnlly the SPM0 as other heavy metals. 6. Countermeasures adopted in the world ai);ainst environmental pollution caused by cadmium- type pigments 6.1 Japan Research in Japan on cadmium and its chemical compounds and countermeasures against environmental pollution in relation to the problems of "itai itai" disease lias progressad rapidly in recûnt years. tfajor pollution standards are as follows. (1) The concentration of cadmium in rice for human consumption should bo under 1 ppm for unhulled rice and under 7.1 .) ppm for polished rice.

(2) The concentration of cadmium in exhaust into the atmosphere should be under 1 mg/Nm3. 18

(3) The concentration of cadmium in water disposal should be under 0.1 ppm.

(4) The concentration of cadmium in drinking water

should 'oe un'ler 3.31 • ppm. (5) When cadmlum in. waste Is under 0.3 mdl it can be treated as a Eeneral waste. When under 0.1 mg/l e it can be disposed in the ocean. The fo11owin7, are standards for cadmium-type pigments used in colouring plastics. (1) Coloured vinyl chloride resin Toys Extracted amount of cadr:Ii'wl in the g-Dpcified extraction test should be under o. 5 pprn. Containers, packing Cadmium content in the specified test should be 100 ppm.

(2) Presently regulations are ln preparation for coloured polyethelene, polypropylene, polyamide and poly- styrene resins. 6.2 America

There Pre. no special regulations for cadmium-type pigments in the U.S.A. lowever, there are some reeulations for cadmium and its compounds. (1) Acco-dingr, to the labour environmental standard,

cadmium in dust should be aner 0. 9 mg/';''13 . Cadriur ox9 nes Phould brve cr1-linn con- * centration lower than 0.1 mg• Nm3 . 1

1 American Conference of Grwernmental Industrial Hygienists 4 19

(2) Cadmium concentration in dr -InIdnc water should p. 1585 be under 0.01 ppm. At present, ADCUA*1 i beinninc to study the *') toxicity of cadmium-type pigments. IL7r,j ` is also interested in the subject as a future study.

E.3 -DIrooe Concernin: cium-type pigments for colourin,1 plastics used in food packa?icur, it is desirable to neet the steniar'' set 13 ?rance. Toavy metals otLer ttial cadmium are also Included In the standards. The amount of soluble

cadmIqr; in 0.1 N hydrochl -,r.:c aci . should be u-1 -7 •r 3.1 In the Italian :,Lanierds the amount is set 3 .2 Tk.ere is no standard in the ot'ler countries of lurope. In r,urope the organization forned by the makers of cadmium pLi.,m- -uits is studying the toxicity of cadmium-type pigments. Results should be reported some time in future. 7. Conclusion As stated above, several studios have been under- teken and cpuntPrmea.curos have been devided with regard to the manufacture of cadmium-type pigments, the colouring process and the handling by users. Uowever, the lack of data is felt strongly.

A mean concentration of O. ppm (Clarke number) of

p. 1:584-

•1 American Dry Cul or Ma nu fact u ring Assoc in Lion +2 International Lead and Zinc lIeseareh Organization cC?dw-^.url is, f7ut1C, in so 11.l in the natural Ç^-at e. LŸlere are. ina:Zy other heavy metals w:-iose poisons are stron`;er than that of C^+1 ii LiC1!. T`_iLref ore it Is n °.cOSsary t.7 j1.t(3gc' the Onviro l-• ment as a '-r1_1J^.e,W?^en stc.n`.2.r^.^s for tnwnLlfacturi^lü and

_land

T'ur•t'Oerï-rio?=e, mercur.,y sulfide is considered Separately from ot'.1er ooi.co_zous men-cu.ry comnounfls and is excluded from snPCS.ficatio^is for violent 2olçonS. rr•o;r, this, it is desirable to study again the safety. of cadmium-type pig:qents ti^ iic'1 arc ti_.)re stcbl^^ <:.s s. w_Z+ol.e' ^ti3 ,^^n ?„e_clzr sùlll^ ,^..a' AlsoA studi es s} oulâ be un^.ertaken to c?.etermine t'^ ° i^2rtlCL;l^+.r can.:rium Con1pJuna.s i•d'[.ic:h cause "ital ital." disCc sE'.. It i s necessary to establish - standard for h.-.n^-11-n,^_; the r?^,r•m- ful cadmium compounds and to define methods f:-:)r• ttleir disposal.

2) Yakoto Tsunashinia, Kazuo TSutSuTf11_ and =T.iroslfii Takahashi.:

^,Tik'za (Jmo<

11 ) )'(1Lln i1 chi ra.nlciLlc!7i f3.nC^. ŸL1k.i.o .^i1Co :Yoi{T70 ( T 2-^aI1 i^- In

Associationl, 60, 417 (1952).

12) For example . . . .

13) For exacriple, Ja-panese Patent, 3E (1 ^61) -5530, (1961)-3830, 33 (10/6_3)-26558.

For exa-m?)l(-;, Ye11ovr tvpe U.S. I'atent, ...

Red type U.S. ?atent. . . .

16) 1.1akito Tsuneshima, i.enzo ',"ori, Kazuo Tsutstuai and

niroshi Taahashi: +(Oka (Tndustrial Chemistry), 74 1773 (1971).

17) .--akoto Tsunashinia, Kenzo Mon, Kazuo Tsutsumi and Hiroshi Talzahashi: Kola (Tndustrial Chemistry) , 74, 1743 (1971). The following are other references On the crystal structure.

1) Gay-Lussac: Ani:. ( hem , el hlys • , 8, 100 (1818) 19) A. L. Edwards, 'I'. E. SI) k house and - 11.0, 2) 1.14)) , iJ f119), 11.41.14 H II, 1, 817 Drickamer: J. P/p.t. 'Mu). .S'tilitit, II, 1-10 • 1959) (1972) 20) IZ.yoichirt; Sato. 11. I tub acid S. : ,/n/an. 3) V.S. Patent, 3, 542, 526 11970) ,1. /'/9..s., 3,626 ;19I,I) 4) A.N. Mariano and E.P. Warekois: Scince, 142, 21) 1).11. 1 lult-and 1).M. 11'ilt ux: ,/. 672 (1963) 9, 193 (1971, A. Jayaraman, W. Klement, Jr. and G.C. 221 ' 0. Liné 5) and M. 1.alittc: svnil.,27, ( , 3:106 Kennedy: ilys. Rev., 130, 2277 (1963) (1963) 6, J.A. Corll: J. _WI. Phy.v., '35, 3032 (1964) 23) M. 0'kt:eft. and F.S. Stunt.: Re. Soc., 267, 7) W.C. Yu and P.). Gielisse: J:t - Bull., G, -.501 (1962) 621 (1971) 8) W.NI. Kane, J.P. Spratt, LW. 1 Iershinger and EH. Khan: J. Elecituchein. Soc., 113, 136 (1966) 9) P. Cherin, EL. Lind and E.A. Davis: J. Elec- truchem. Soc., 117, 233 (1970) 10) A. J. Eroles and AI.. Friedberg; J. .11n.( lam. Suc., 43, 233 (1965) 11) di Ili (te ;•)(, .F.11 : 60, .117 11952) 12) h ; U.S. Patent 2, 850, 400., 2,850, 101, 2,850, 402 (1956), 2,11711, 13.1 (19551, 3,008, 845 (1960) 13) f, LI:, II ,PVIA.. iq't '36 5530. 36 3830, O( 38 .26558. 14) U.S. Patent 3,012, 899, 15) le:, "AL -.fz U. S. Patent 2, 059, -121, 2, 061, 368, 2, 406, 472, 2,607, 705, 2,819, 175. Czech. Patent 97, 866. et U. S. Patent 1, 894, 931, 2, 226, 573. 2, 419, 027, 2, 479, 636, 2,501, 147, 2.517, 59.1, 2,523, 119, G. Patent 621, 854, 16) 110, Si. Ili 9), . 74, 1773 (1971) 17) iAn a. l Çii9J, ,;'e.r, 74, 1740 (1471) •/-) h ;;'J‘: 1: it; t • 18) M.A. Short and E.G. Steward: Ant. Alin., 44, 189 (1959)