Selective sulphuratiun processes, which occurred when copper or one of some copper alloys (Alumihrass I, II, K. M. C., Admiralty) was reacted with H₂S-gas or sulphur vapour under vark; us conditions, were studied by electron diffraction method and there were observed several sulphides of metals such as CuS, Cu_1⋅8S, Cu₂S, α-ZnS, β-ZnS and Al₂S₃.
The conditions of temperature and pressure of the gas or the vapour forr the formation of each sulphide were determined as shown in rFahle 2 and Fig3. 4-10. The sulphide ZnS or AI₂S₃, forrned on he surface of the specimens prevented further sulphuration of the metals.
In some cases several kinds of sulphides formed layers which covered the surfaces of the specimen.

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Using the method of analysis same as that described in the previous two reports²⁾³⁾ on calcium and strontium formates, the crystal structure of barium and lead formates was determined. Both crystals correspond to the same space group D⁴₂-P2₁2₁2₁as strontium formate. The dimensions of the unit cell containing four chemical units are: a=6.80 kX, b=8.89 kX, c= 7.66 kX for Ba (HCO₂) ₂, a=6.52 kX, b=8.75 kX, c=7.41 kX for Pb (HCO₂) ₂. All the atoms occupy sets of general positions : xyz; 1/2+x, 1/2-y, -z; 1/2-x, 1/2+y, 1/2-z; -x, -y, 1/2+z. By means of the syntheses of the two-dimensional Patterson functions and electron densities, the atomic parameters were obtained (see Table 4), their final adjustment being made by intensity calculations.
The determined structure of these crystals was discussed comparing with those of Sr (HCO₂) ₂and Ca (HCO₂) ₂, of which the latter corresponds to D¹⁵_2h-Pcabwith the unit cell containing eight chemical units. In all these crystals (HCO₂) ^- ion possesses approximately the same structure, its two C-O distances being practically the same, thus showing almost complete resonance between the two valence bond structures for (HCO₂) ^- .
App. The thermal expansion coefficients of anhydrous strontium formate along the three principal axes were measured by the method of the high angle X-ray reflection. The values between 23°-76°C are : a_a= (3.57±0.08) ×10^-5, a_b= (1.15 ±0.05) ×10^-3, a_e= (2.36±0.05) ×10^-5.

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The intensity formula for the X-ray diffraction by a one-dimensionally disordered crystal was obtained using the matrix-method of Hendricks and Teller for the case of a finite number N of layers (eqs. (15), (16) ) . Deviding (15) by N and putting N→∞, the agreement is obtained between (15) and eq. [29] in their paper, their ∅ ^(s) and V^(s) being correlated with our ∅_sand V_s by (20) .The general formula for S=0 (S is the degree of influence of the preceding layers on P_st) is (25) or (26) . Using the relation (27), the term with N in (26) is equal to [20] of Hendricks & Teller. For the special value of ∅_s, of (28) the denominators in (26) become 0, in which case (25) becomes (29) and, while only the first term with N in (26) becomes (30) in the limiting value of γ→Γ and is generally very weak, the limiting value of the whole (26) becomes equal to (29) . In case S=0 and ∅_s=∅ (26) becomes (32) . In case S=0 and V_s=V, we obtain (36) and (37) . The general formula for S=1 is (15) or (16) itself, which can be, if wanted, separated into two parts, one due to S=0 and the other to S=1, by using (42) or (43) . In case S=1 and ∅_s=∅ (15) becomes (49), which turns out (53) for R=2. For a one-dimensional AB-alloy (53) becomes (56) which is equal to (57) in the complete disorder and to (58) or (59) in the perfect order. The agreement can be obtained between (15) and (38) used by Wilson ²⁾ and Jagodzinski ³⁾ by introducing (40) . S_jS^∗_j+ngiven by them for S=1, (60), can be obtained from (40) by taking the special value of (61) for P, which is available only for the close-packed structure. The difference equations for P_n for, S=2 and 3 used by the mwill be obtained from a set of 2^s-2simultaneous difference equations for S=S, which will be described in the third report. In conclusion, in order to examine only the general feature of the diffuse scattering we are satisfied only with the term with N in (16) but we should consider the higher term when we examine for example, the relation between the diffuse and Laue scatterings, the crystal with slight irregularities, the intensity near the special point ( (28) ), or specially the crystal with small N (Fig.1.) .

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